Integrate Monolog: replace four logging systems with single PSR-3 factory

- Add monolog/monolog dependency (^3.10)  
- Create app/Logger.php central factory with channels: app, admin, error, audit
- Each channel gets RotatingFileHandler (30-day retention) with pass-through LineFormatter
  preserving existing JSON format contracts
- Rewrite AppLogger as thin facade delegating to Logger::get('app')
- Rewrite ErrorHandler::log() to delegate to Logger::get('error')
- Rewrite AdminLogger file output to delegate to Logger::get('admin'), keep DB writes
- Add Monolog file shadow to Audit via Logger::get('audit') (Option A per monolog-plan)
- Log level controlled by LOG_LEVEL env var (defaults: DEBUG in cli-server, WARNING otherwise)
- Graceful NullHandler fallback when log directory is not writable
- Update SystemController LOG_FILES: remove php_error, add app/admin/error/audit
- JSON app logs parsed to readable one-liners in the log viewer
- Remove nginx config tab (parametres + fragment + template + css)
- Friendly empty-state message when app log files don't exist yet (notYet)
- PHP tail fallback when exec() unavailable
- All 228 PHPUnit tests pass, no call sites changed

TODO.md

@@ -225,8 +225,12 @@
 - [x] Step 4 — Update templates (data-queue-type on all inputs, data-existing-files in edit)
 - [x] Step 5 — Update upload-progress.js (new collectFileNames, pending-uploads guard)
 - [ ] Step 6 — QA / integration testing
+- [x] Logs accessible via Paramètres: app, admin, error, audit tabs (JSON parsed to readable lines), nginx tabs kept
+- [x] Remove nginx config tab and PHP-FPM error log tab from UI
 - [ ] Step 7 — Cleanup: remove transition flags, remove INPUT_ID_TO_TYPE
 
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 # CSP & Deploy Fixes (May 2026)
 
 - [x] Track vendor JS files in jj (they were moved to vendor/ but never `jj file track`ed)