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>

tests/Feature/Database/RenameFoldersToDeclarationsTest.php

@@ -36,8 +36,8 @@ test('composite index exists on messages declaration_id and created_at', functio
 });
 
 test('migration is reversible and rollback restores folder tables', function () {
-    // Rollback the rename migration (last one applied)
-    $this->artisan('migrate:rollback', ['--step' => 1]);
+    // Rollback foundation migrations (3) + polymorphic update + rename migration
+    $this->artisan('migrate:rollback', ['--step' => 5]);
 
     expect(Schema::hasTable('folders'))->toBeTrue();
     expect(Schema::hasTable('declarations'))->toBeFalse();