feat: L'Ami Fiduciaire V1.0.0 — full codebase with Story 0.1 complete

Initial commit of the L'Ami Fiduciaire SaaS platform built on Laravel 12,
Vue 3, Inertia.js 2, and Tailwind CSS 4.

Story 0.1 (rename folders to declarations in database) is implemented and
code-reviewed: migration, rollback, and 6 Pest tests all passing.

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

app/Http/Controllers/FolderMentionController.php

@@ -0,0 +1,59 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Http\Requests\StoreFolderMentionRequest;
+use App\Models\Folder;
+use App\Models\User;
+use App\Models\Workspace;
+use App\Notifications\FolderMentionNotification;
+use Illuminate\Http\RedirectResponse;
+use Illuminate\Http\Request;
+use Illuminate\Support\Facades\Cache;
+
+class FolderMentionController extends Controller
+{
+    protected function currentWorkspace(Request $request): Workspace
+    {
+        $workspaceId = $request->session()->get('current_workspace_id');
+
+        return Workspace::query()->findOrFail($workspaceId);
+    }
+
+    protected function authorizeFolder(Workspace $workspace, Folder $folder): void
+    {
+        if ($folder->workspace_id !== $workspace->id) {
+            abort(404);
+        }
+    }
+
+    public function store(StoreFolderMentionRequest $request, Folder $folder): RedirectResponse
+    {
+        $workspace = $this->currentWorkspace($request);
+        $this->authorizeFolder($workspace, $folder);
+
+        $userRole = $workspace->users()
+            ->where('users.id', $request->user()->id)
+            ->first()
+            ?->pivot
+            ?->role
+            ?->value;
+
+        if (! in_array($userRole, ['owner', 'manager'])) {
+            abort(403);
+        }
+
+        $validated = $request->validated();
+        $targetUser = User::findOrFail($validated['user_id']);
+
+        $targetUser->notify(new FolderMentionNotification(
+            $folder,
+            $request->user(),
+            $validated['message'],
+        ));
+
+        Cache::forget("user:{$targetUser->id}:unread_notifications");
+
+        return back()->with('flash', ['type' => 'success', 'message' => 'Notification envoyée.']);
+    }
+}