* [mod] client/simple: client plugins

Defines a new interface for client side *"plugins"* that coexist with server
side plugin system. Each plugin (e.g., `InfiniteScroll`) extends the base
`ts Plugin`. Client side plugins are independent and lazy‑loaded via `router.ts`
when their `load()` conditions are met. On each navigation request, all
applicable plugins are instanced.

Since these are client side plugins, we can only invoke them once DOM is fully
loaded. E.g. `Calculator` will not render a new `answer` block until fully
loaded and executed.

For some plugins, we might want to handle its availability in `settings.yml`
and toggle in UI, like we do for server side plugins. In that case, we extend
`py Plugin` instancing only the information and then checking client side if
[`settings.plugins`](https://github.com/inetol/searxng/blob/1ad832b1dc33f3f388da361ff2459b05dc86a164/client/simple/src/js/toolkit.ts#L134)
array has the plugin id.

* [mod] client/simple: rebuild static

Previously, when using a search url copied from the cookies tab, clicking
at the settings icon at the top right would show the browser preferences
and not the preferences that were set and used with the search url.
Please see https://github.com/searxng/searxng/issues/5227 for more information.

To test:
- change some preferences
- copy the preferences search url in the settings' cookies tab
- reset the preferences or clear cookies
- paste the copied search url into the search bar to search for something
- press the settings icon
- you can now see/preview the actual settings that were used for the search
- by pressing 'save', you can keep these preferences

closes #5227

To avoid an `unsafe-inline` in the CSP header, the JS code must be moved to the
client side [1].

The `<script>` tag at the end of the HTML originates from the old implementation
of the JS client. Since PR-5073 [2] was merged, the `type` is now `module`, and
the tag must be moved to the beginning of the HTML.

> We need to inline this "JS is enabled?" thing to prevent layout shifts and
> temporary "no JS enabled" visuals as ESM scripts loads and evals everything
> deferred from initial DOM render [3]

That's true in theory, but in practice, this effect is unnoticeable because it's
masked by another effect (which we can't avoid): If we load the page with a
severely throttled connection, the HTML (result list) takes a long time to
load. Then the CSS is loaded, which also takes longer. Until the CSS has loaded,
there's no layout. A layout shift is therefore largely determined by the loading
of the HTML and CSS itself.

The running times of the ESM script can be neglected compared to the loading
times of HTML & CSS.

[1] https://github.com/searxng/searxng-docker/pull/424#issuecomment-3199494256
[2] https://github.com/searxng/searxng/pull/5073
[3] https://github.com/searxng/searxng-docker/pull/424#issuecomment-3199622504

Lay the foundation for loading scripts granularly depending on the endpoint it's
on.

Remove vendor specific prefixes as there are now managed by browserslist and
LightningCSS.

Enabled quite a few rules in Biome that don't come in recommended to better
catch issues and improve consistency.

Related:

- https://github.com/searxng/searxng/pull/5073#discussion_r2256037965
- https://github.com/searxng/searxng/pull/5073#discussion_r2256057100

TypeScript is a superset of JavaScript, converting the entire theme to
TypeScript allows us to receive much more feedback on possible issues made in
package updates or our own typos, furthermore, it allows to transpile properly
to lower specs. This PR couldn't be done in smaller commits, a lot of work
needed to make everything *work properly*:

- A browser baseline has been set that requires minimum **Chromium 93, Firefox
  92 and Safari 15** (proper visuals/operation on older browser versions is not
  guaranteed)
- LightningCSS now handles minification and prefix creation for CSS.
- All hardcoded polyfills and support for previous browser baseline versions
  have been removed.
- Convert codebase to TypeScript.
- Convert IIFE to ESM, handling globals with IIFE is cumbersome, ESM is the
  standard for virtually any use of JS nowadays.
- Vite now builds the theme without the need for `vite-plugin-static-copy`.
- `searxng.ready` now accepts an array of conditions for the callback to be
  executed.
- Replace `leaflet` with `ol` as there were some issues with proper Vite
  bundling.
- Merged `head` with `main` script, as head was too small now.
- Add `assertElement` to properly check the existence of critical DOM elements.
- `searxng.on` renamed to `searxng.listen` with some handling improvements.

This patch implements the template generation of the template:

  searx/templates/simple/icons.html

by the way the icon set (the icon names) has been normalized:

  film-outline   --> film
  magnet-outline --> magnet
  ..
  warning        --> alert

Some missing (categorie) icons had been added.

Some of the ionicons are not suitable for a dark theme, we fixed the svg
manually in src/svg/ionicons:

- https://github.com/searxng/searxng/pull/4284#issuecomment-2680550342

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

Typification of SearXNG
=======================

This patch introduces the typing of the results.  The why and how is described
in the documentation, please generate the documentation ..

    $ make docs.clean docs.live

and read the following articles in the "Developer documentation":

- result types --> http://0.0.0.0:8000/dev/result_types/index.html

The result types are available from the `searx.result_types` module.  The
following have been implemented so far:

- base result type: `searx.result_type.Result`
  --> http://0.0.0.0:8000/dev/result_types/base_result.html

- answer results
  --> http://0.0.0.0:8000/dev/result_types/answer.html

including the type for translations (inspired by #3925).  For all other
types (which still need to be set up in subsequent PRs), template documentation
has been created for the transition period.

Doc of the fields used in Templates
===================================

The template documentation is the basis for the typing and is the first complete
documentation of the results (needed for engine development).  It is the
"working paper" (the plan) with which further typifications can be implemented
in subsequent PRs.

- https://github.com/searxng/searxng/issues/357

Answer Templates
================

With the new (sub) types for `Answer`, the templates for the answers have also
been revised, `Translation` are now displayed with collapsible entries (inspired
by #3925).

    !en-de dog

Plugins & Answerer
==================

The implementation for `Plugin` and `Answer` has been revised, see
documentation:

- Plugin: http://0.0.0.0:8000/dev/plugins/index.html
- Answerer: http://0.0.0.0:8000/dev/answerers/index.html

With `AnswerStorage` and `AnswerStorage` to manage those items (in follow up
PRs, `ArticleStorage`, `InfoStorage` and .. will be implemented)

Autocomplete
============

The autocompletion had a bug where the results from `Answer` had not been shown
in the past.  To test activate autocompletion and try search terms for which we
have answerers

- statistics: type `min 1 2 3` .. in the completion list you should find an
  entry like `[de] min(1, 2, 3) = 1`

- random: type `random uuid` .. in the completion list, the first item is a
  random UUID

Extended Types
==============

SearXNG extends e.g. the request and response types of flask and httpx, a module
has been set up for type extensions:

- Extended Types
  --> http://0.0.0.0:8000/dev/extended_types.html

Unit-Tests
==========

The unit tests have been completely revised.  In the previous implementation,
the runtime (the global variables such as `searx.settings`) was not initialized
before each test, so the runtime environment with which a test ran was always
determined by the tests that ran before it.  This was also the reason why we
sometimes had to observe non-deterministic errors in the tests in the past:

- https://github.com/searxng/searxng/issues/2988 is one example for the Runtime
  issues, with non-deterministic behavior ..

- https://github.com/searxng/searxng/pull/3650
- https://github.com/searxng/searxng/pull/3654
- https://github.com/searxng/searxng/pull/3642#issuecomment-2226884469
- https://github.com/searxng/searxng/pull/3746#issuecomment-2300965005

Why msgspec.Struct
==================

We have already discussed typing based on e.g. `TypeDict` or `dataclass` in the past:

- https://github.com/searxng/searxng/pull/1562/files
- https://gist.github.com/dalf/972eb05e7a9bee161487132a7de244d2
- https://github.com/searxng/searxng/pull/1412/files
- https://github.com/searxng/searxng/pull/1356

In my opinion, TypeDict is unsuitable because the objects are still dictionaries
and not instances of classes / the `dataclass` are classes but ...

The `msgspec.Struct` combine the advantages of typing, runtime behaviour and
also offer the option of (fast) serializing (incl. type check) the objects.

Currently not possible but conceivable with `msgspec`: Outsourcing the engines
into separate processes, what possibilities this opens up in the future is left
to the imagination!

Internally, we have already defined that it is desirable to decouple the
development of the engines from the development of the SearXNG core / The
serialization of the `Result` objects is a prerequisite for this.

HINT: The threads listed above were the template for this PR, even though the
implementation here is based on msgspec.  They should also be an inspiration for
the following PRs of typification, as the models and implementations can provide
a good direction.

Why just one commit?
====================

I tried to create several (thematically separated) commits, but gave up at some
point ... there are too many things to tackle at once / The comprehensibility of
the commits would not be improved by a thematic separation. On the contrary, we
would have to make multiple changes at the same places and the goal of a change
would be vaguely recognizable in the fog of the commits.

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

Removes ``/>`` ending tags for void elements [1] and replaces them with ``>``.
Part of the larger cleanup to cleanup invalid HTML throughout the codebase [2].

[1] https://html.spec.whatwg.org/multipage/syntax.html#void-elements
[2] https://github.com/searxng/searxng/issues/3793