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/Http/Requests/StoreDeclarationMessageRequest.php

@@ -0,0 +1,54 @@
+<?php
+
+namespace App\Http\Requests;
+
+use App\Enums\MessageType;
+use BenSampo\Enum\Rules\EnumValue;
+use Illuminate\Foundation\Http\FormRequest;
+
+class StoreDeclarationMessageRequest extends FormRequest
+{
+    /**
+     * Determine if the user is authorized to make this request.
+     */
+    public function authorize(): bool
+    {
+        return $this->user() !== null;
+    }
+
+    /**
+     * Get the validation rules that apply to the request.
+     *
+     * @return array<string, \Illuminate\Contracts\Validation\ValidationRule|array<mixed>|string>
+     */
+    public function rules(): array
+    {
+        $rules = [
+            'type' => ['required', new EnumValue(MessageType::class)],
+            'body' => ['required', 'string', 'max:65535'],
+            'files' => ['nullable', 'array'],
+            'files.*' => ['file', 'max:10240'], // 10MB per file
+        ];
+
+        $type = $this->input('type');
+
+        if (in_array($type, ['situation', 'confirmation'])) {
+            $rules['files'] = ['required', 'array', 'min:1'];
+        }
+
+        return $rules;
+    }
+
+    /**
+     * Get custom attributes for validator errors.
+     *
+     * @return array<string, string>
+     */
+    public function attributes(): array
+    {
+        return [
+            'body' => 'message',
+            'files' => 'fichiers',
+        ];
+    }
+}