feat: complete Epic 0 — foundation migration & infrastructure setup

Stories 0.2-0.5: rename folders→declarations (backend+frontend), configure
Redis for cache/queue/sessions, add foundation database migrations
(permissions, archived_at), replace DeclarationStatus enum with architecture
lifecycle values, create DeclarationObserver for status transition validation
and auto-archive, fix controller status transitions to respect observer rules.

93 tests pass (240 assertions).

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

app/Notifications/FolderMentionNotification.php

@@ -1,56 +0,0 @@
-<?php
-
-namespace App\Notifications;
-
-use App\Models\Folder;
-use App\Models\User;
-use Illuminate\Bus\Queueable;
-use Illuminate\Contracts\Queue\ShouldQueue;
-use Illuminate\Notifications\Messages\MailMessage;
-use Illuminate\Notifications\Notification;
-
-class FolderMentionNotification extends Notification implements ShouldQueue
-{
-    use Queueable;
-
-    public function __construct(
-        public Folder $folder,
-        public User $mentionedBy,
-        public string $message,
-    ) {}
-
-    /**
-     * @return array<string>
-     */
-    public function via(object $notifiable): array
-    {
-        return ['database', 'mail'];
-    }
-
-    /**
-     * @return array<string, mixed>
-     */
-    public function toDatabase(object $notifiable): array
-    {
-        return [
-            'folder_id' => $this->folder->id,
-            'folder_title' => $this->folder->title,
-            'mentioned_by_id' => $this->mentionedBy->id,
-            'mentioned_by_name' => $this->mentionedBy->name,
-            'message' => $this->message,
-            'url' => route('folders.show', $this->folder),
-        ];
-    }
-
-    public function toMail(object $notifiable): MailMessage
-    {
-        return (new MailMessage)
-            ->subject('Vous avez été mentionné - '.$this->folder->title)
-            ->markdown('emails.folder-mention', [
-                'folderTitle' => $this->folder->title,
-                'mentionedByName' => $this->mentionedBy->name,
-                'message' => $this->message,
-                'url' => route('folders.show', $this->folder),
-            ]);
-    }
-}