feat: FASE 1 - Backend Core (modelli, auth, API)

Implementazione completa del backend FastAPI:
- Modelli SQLAlchemy: User, Recipe, RecipeVersion, RecipeTask,
  RecipeSubtask, Measurement, AccessLog, SystemSetting, RecipeVersionAudit
- Schemas Pydantic v2 per tutti i CRUD + statistiche SPC
- Middleware: API Key auth (X-API-Key) con role checking + access logging
- Router: auth, users, recipes, tasks, measurements, files, settings
- Services: auth (bcrypt+secrets), recipe (copy-on-write versioning),
  measurement (auto pass/fail con UTL/UWL/LWL/LTL)
- Alembic env.py con import modelli attivi
- Fix architect review: no double-commit, recipe_id subquery filter,
  user_id in access logs, type annotations corrette

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/middleware/logging.py

@@ -0,0 +1,54 @@
+"""Access logging middleware for FastAPI."""
+import time
+from typing import Callable
+
+from fastapi import Request, Response
+from starlette.middleware.base import BaseHTTPMiddleware
+from sqlalchemy import insert
+
+from database import async_session_factory
+from models.access_log import AccessLog
+
+
+class AccessLogMiddleware(BaseHTTPMiddleware):
+    """Middleware that logs every API request to the access_logs table."""
+
+    # Paths to exclude from logging (health checks, static files)
+    EXCLUDED_PATHS = {"/api/health", "/docs", "/openapi.json", "/redoc"}
+
+    async def dispatch(self, request: Request, call_next: Callable) -> Response:
+        # Skip excluded paths
+        if request.url.path in self.EXCLUDED_PATHS:
+            return await call_next(request)
+
+        start_time = time.time()
+        response = await call_next(request)
+        duration_ms = (time.time() - start_time) * 1000
+
+        # Extract user info from request state (set by auth middleware)
+        user_id = getattr(request.state, "user_id", None)
+
+        # Log asynchronously (don't block response)
+        try:
+            async with async_session_factory() as session:
+                await session.execute(
+                    insert(AccessLog).values(
+                        user_id=user_id,
+                        action=f"{request.method} {request.url.path}",
+                        details={
+                            "method": request.method,
+                            "path": request.url.path,
+                            "query": str(request.query_params),
+                            "status_code": response.status_code,
+                            "duration_ms": round(duration_ms, 2),
+                        },
+                        ip_address=request.client.host if request.client else None,
+                        user_agent=request.headers.get("user-agent", "")[:500],
+                    )
+                )
+                await session.commit()
+        except Exception:
+            # Don't fail the request if logging fails
+            pass
+
+        return response