perf: Fix all 7 code analysis issues

HIGH (Performance):
- Replace 8 sync file operations with aiofiles in async context (storage, mail,
  report_generator, dms_bridge, ai_assistant)
- Frontend bundle splitting: manualChunks for react-vendor, ui-components, tanstack,
  markdown, icons, utils, i18n (ui chunk 936K → ~19K)

MEDIUM (Architecture):
- Worker circular deps: Replace direct plugin imports with job_registry.py pattern
  (register_job/get_all_jobs, importlib-based lazy loading)
- App-wide ErrorBoundary: New ErrorBoundary.tsx component, wrapped in AppShell
  and all standalone routes

LOW (Code Quality):
- N+1 query fix: selectinload(Contact.contact_persons) in list_contacts()
- O(n²) dedup fix: SQL GROUP BY for email/phone duplicates, Dict-based name grouping
- Response format standardization: 7 routes converted from plain arrays to
  {items: [...], total: N} format

app/plugins/builtins/ai_assistant/routes.py

@@ -6,6 +6,7 @@ from __future__ import annotations
 
 import uuid
 
+import aiofiles
 from fastapi import APIRouter, Depends, HTTPException, Query, UploadFile
 from fastapi.responses import FileResponse, StreamingResponse
 from sqlalchemy import select
@@ -407,7 +408,8 @@ async def list_tools(
     current_user: dict = Depends(get_current_user),
 ):
     registry = get_tool_registry()
-    return registry.list_for_api()
+    items = registry.list_for_api()
+    return {"items": items, "total": len(items)}
 
 
 # ─── Chat Sessions ───
@@ -717,8 +719,8 @@ async def upload_attachment(
     file_id = str(uuid.uuid4())
     safe_filename = file.filename or "unnamed"
     storage_path = str(ATTACHMENT_DIR / f"{file_id}_{safe_filename}")
-    with open(storage_path, "wb") as f:
-        f.write(content)
+    async with aiofiles.open(storage_path, "wb") as f:
+        await f.write(content)
 
     attachment = AIChatAttachment(
         session_id=session.id,

app/plugins/builtins/ai_assistant/services.py

@@ -12,6 +12,8 @@ import logging
 import uuid
 from typing import Any, AsyncGenerator
 
+import aiofiles
+
 import litellm
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -380,8 +382,8 @@ async def _extract_attachment_content(
     parts: list[str] = []
     for att in attachments:
         try:
-            with open(att.storage_path, "rb") as f:
-                content = f.read()
+            async with aiofiles.open(att.storage_path, "rb") as f:
+                content = await f.read()
 
             text_content = ""
             mime = att.mime_type.lower()