Fix admin AI nav bug, add rescan feature

- Fix Blade parse error in admin AI settings (Blade was interpreting
  JSON braces in DEFAULT_PROMPT as template tags, breaking the navbar)
  — pass defaultPrompt from controller instead
- Add rescan: POST /nail-polishes/{id}/rescan creates a new import for
  an existing nail polish and updates its fields after AI analysis
- Add KI-Rescan button on collection cards (only if image exists)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

routes/web.php

@@ -69,6 +69,7 @@ Route::middleware(['auth'])->group(function () {
     // KI Foto-Import (für alle eingeloggten User)
     Route::resource('nail-polish-imports', NailPolishImportController::class)
         ->only(['index', 'create', 'store', 'show']);
+    Route::post('/nail-polishes/{nailPolish}/rescan', [NailPolishImportController::class, 'rescan'])->name('nail-polishes.rescan');
 });
 
 // Fallback