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/Enums/DeclarationPriority.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace App\Enums;
+
+use BenSampo\Enum\Enum;
+
+final class DeclarationPriority extends Enum
+{
+    const Low = 'low';
+
+    const Medium = 'medium';
+
+    const High = 'high';
+}