refactor : simplify codebase and fix critical issues

Backend:
- Add MCP Serializer to centralize entity-to-array conversion (~300 lines deduped)
- Fix race condition in task/ticket number generation (SELECT FOR UPDATE + transaction)
- Add unique constraint on task (project_id, number) with migration
- Fix MIME type validation: use server-detected finfo instead of client-supplied type
- Add allowlist of permitted MIME types for uploads
- Fix TaskDocumentDownloadController: allow ROLE_CLIENT access, add priority:1
- Fix notification sent even when ticket status unchanged
- Remove redundant exception constructors
- Simplify services (BookStackApi double fetch, TokenEncryptor, GiteaApi)
- Consolidate duplicate checks in processors

Frontend:
- Fix useApi isHandlingUnauthorized scope (module-level to prevent double 401 redirect)
- Fix client-tickets toast key copy-paste bug
- Merge duplicated tasks service methods (getByProject + getByProjectArchived)
- Extract shared uploadWithRelation helper in task-documents service
- Extract formatFileSize utility from duplicated component code
- Extract status transition logic into useClientTicketHelpers composable
- Remove dead code (unused router, handleLogout, empty script blocks)
- Merge duplicate watchers and onMounted calls
- Normalize arrow functions to function declarations per convention

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Mcp/Tool/Task/UpdateTaskTool.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace App\Mcp\Tool\Task;
 
+use App\Mcp\Tool\Serializer;
 use App\Repository\TaskEffortRepository;
 use App\Repository\TaskGroupRepository;
 use App\Repository\TaskPriorityRepository;
@@ -114,38 +115,14 @@ class UpdateTaskTool
             'number'      => $task->getNumber(),
             'title'       => $task->getTitle(),
             'description' => $task->getDescription(),
-            'status'      => $task->getStatus() ? [
-                'id'    => $task->getStatus()->getId(),
-                'label' => $task->getStatus()->getLabel(),
-                'color' => $task->getStatus()->getColor(),
-            ] : null,
-            'priority' => $task->getPriority() ? [
-                'id'    => $task->getPriority()->getId(),
-                'label' => $task->getPriority()->getLabel(),
-                'color' => $task->getPriority()->getColor(),
-            ] : null,
-            'effort' => $task->getEffort() ? [
-                'id'    => $task->getEffort()->getId(),
-                'label' => $task->getEffort()->getLabel(),
-            ] : null,
-            'assignee' => $task->getAssignee() ? [
-                'id'       => $task->getAssignee()->getId(),
-                'username' => $task->getAssignee()->getUsername(),
-            ] : null,
-            'group' => $task->getGroup() ? [
-                'id'    => $task->getGroup()->getId(),
-                'title' => $task->getGroup()->getTitle(),
-            ] : null,
-            'project' => [
-                'id'   => $task->getProject()->getId(),
-                'code' => $task->getProject()->getCode(),
-                'name' => $task->getProject()->getName(),
-            ],
-            'tags' => $task->getTags()->map(fn ($t) => [
-                'id'    => $t->getId(),
-                'label' => $t->getLabel(),
-            ])->toArray(),
-            'archived' => $task->isArchived(),
+            'status'      => Serializer::status($task->getStatus()),
+            'priority'    => Serializer::priority($task->getPriority()),
+            'effort'      => Serializer::effort($task->getEffort()),
+            'assignee'    => Serializer::user($task->getAssignee()),
+            'group'       => Serializer::groupRef($task->getGroup()),
+            'project'     => Serializer::projectRef($task->getProject()),
+            'tags'        => Serializer::tags($task->getTags()),
+            'archived'    => $task->isArchived(),
         ]);
     }
 }