feat: add unified linting scripts and git hooks for code quality enforcement

- Introduced `lint` and `lint-fix` applications in `flake.nix` for unified linting of backend (Python) and frontend (TypeScript/Svelte) code.
- Added `scripts/lint.sh` for manual linting execution.
- Created `scripts/install-hooks.sh` to set up git hooks for automatic linting before commits and optional tests before pushes.
- Updated `README.md` with instructions for using the new linting features and git hooks.

backend/app/main.py

@@ -5,6 +5,7 @@ import logging
 from fastapi import FastAPI, Request
 from fastapi.responses import JSONResponse
 
+from app.api import auth
 from app.core.config import settings
 from app.core.errors import WebRefException
 from app.core.logging import setup_logging
@@ -81,7 +82,6 @@ async def root():
 
 
 # API routers
-from app.api import auth
 app.include_router(auth.router, prefix=f"{settings.API_V1_PREFIX}")
 # Additional routers will be added in subsequent phases
 # from app.api import boards, images
@@ -101,4 +101,3 @@ async def startup_event():
 async def shutdown_event():
     """Application shutdown tasks."""
     logger.info(f"Shutting down {settings.APP_NAME}")
-