refactor: Cleanup git state - commit all staged changes

Major refactoring cleanup:
- Add new controller architecture (class-controller-*.php)
- Add new settings-v2 UI (views/settings-v2/)
- Add new CSS architecture (agentic-sidebar.css, tokens)
- Add esbuild build pipeline (scripts/build.js, package.json)
- Add composer dependencies (vendor/)
- Add frontend src directory (assets/js/src/index.jsx)
- Add documentation files
- Remove old/obsolete files (class-settings.php, old CSS)

This commits all pending changes from previous refactoring efforts.

vendor/symfony/contracts/Deprecation/README.md

@@ -0,0 +1,26 @@
+Symfony Deprecation Contracts
+=============================
+
+A generic function and convention to trigger deprecation notices.
+
+This package provides a single global function named `trigger_deprecation()` that triggers silenced deprecation notices.
+
+By using a custom PHP error handler such as the one provided by the Symfony ErrorHandler component,
+the triggered deprecations can be caught and logged for later discovery, both on dev and prod environments.
+
+The function requires at least 3 arguments:
+ - the name of the Composer package that is triggering the deprecation
+ - the version of the package that introduced the deprecation
+ - the message of the deprecation
+ - more arguments can be provided: they will be inserted in the message using `printf()` formatting
+
+Example:
+```php
+trigger_deprecation('symfony/blockchain', '8.9', 'Using "%s" is deprecated, use "%s" instead.', 'bitcoin', 'fabcoin');
+```
+
+This will generate the following message:
+`Since symfony/blockchain 8.9: Using "bitcoin" is deprecated, use "fabcoin" instead.`
+
+While not recommended, the deprecation notices can be completely ignored by declaring an empty
+`function trigger_deprecation() {}` in your application.