Replace Psalm with PHPStan + PHP‑CS‑Fixer + Biome, add linting configs & cleanup

- Removed the `vimeo/psalm` dependency and all related files
(`psalm.xml`, `psalm‑baseline.xml`, suppress annotations).  
- Added **PHPStan** (v2.1.54) and **PHP‑CS‑Fixer** (v3.95.1) to
`vendor/bin/`.  
- Created `phpstan.neon` (level 5, bootstraps `app/bootstrap.php`,
scans `Parsedown.php`).  
- Created `phpstan‑baseline.neon` with 10 pre‑existing errors.  
- Added `.php‑cs‑fixer.dist.php` (PSR‑12 + PHP80Migration, targets
 `app/src` & `app/tests`).  
- Added `biome.json` and updated `justfile` to replace the old Psalm
recipes with `phpstan`, `cs‑check`, and `cs‑fix`.  
- Updated `.gitignore` to exclude PHPStan and PHP‑CS‑Fixer cache files.  
- Updated several JS files (`file‑preview.js`, `file‑upload‑queue.js`)
eand PHP controllers (`MediaController.php`, `SearchController.php`,
`SystemController.php`).  
- Minor adjustments to `TODO.md`, `app/src/Database.php`,
`app/src/Parsedown.php`, `app/src/ShareLink.php`, and
`app/src/SmtpRelay.php`.

justfile

@@ -84,6 +84,22 @@ test:
     #   php app/tests/Integration/SearchTest.php
     @php app/tests/run-tests.php
 
+[group('test')]
+lint-biome:
+    @biome lint app/public/assets/js/file-preview.js app/public/assets/js/file-upload-queue.js
+
+[group('test')]
+phpstan:
+    @vendor/bin/phpstan analyse --memory-limit=512M
+
+[group('test')]
+cs-check:
+    @vendor/bin/php-cs-fixer check --no-interaction
+
+[group('test')]
+cs-fix:
+    @vendor/bin/php-cs-fixer fix --no-interaction
+
 [group('test')]
 syntax:
     @find app/ -name '*.php' -exec php -l {} \; 2>/dev/null | grep -v 'No syntax errors' || true