feat: complete web application — FastAPI backend + Vue 3 SPA frontend

- Full FastAPI backend with JWT auth, file management, processing pipeline,
  memory CRUD, barcode mappings, config management, cloud sync
- Vue 3 + Element Plus frontend with dashboard, task history, HTTP logs,
  memory editor, barcode editor, config editor, sync page
- HTTP request logging middleware with SQLite persistence
- Task history tracking with progress and retry support
- File metadata recording for upload/download operations
- WebAuth section in config.ini for bcrypt password storage
- Bug fix: logs.py count query returns tuple not dict

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/backend/services/db_pool.py

@@ -0,0 +1,20 @@
+"""SQLite write serialization for async context"""
+
+import asyncio
+from typing import Callable, Any
+
+
+class DBPool:
+    """Serializes SQLite writes via asyncio.Lock. Reads are concurrent."""
+
+    def __init__(self):
+        self._write_lock = asyncio.Lock()
+
+    async def execute_write(self, fn: Callable, *args, **kwargs) -> Any:
+        async with self._write_lock:
+            loop = asyncio.get_event_loop()
+            return await loop.run_in_executor(None, lambda: fn(*args, **kwargs))
+
+    async def execute_read(self, fn: Callable, *args, **kwargs) -> Any:
+        loop = asyncio.get_event_loop()
+        return await loop.run_in_executor(None, lambda: fn(*args, **kwargs))