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/api_key.py

@@ -0,0 +1,71 @@
+"""API Key authentication dependency for FastAPI."""
+from fastapi import Depends, HTTPException, Request, status
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from database import get_db
+from models.user import User
+
+
+async def get_current_user(
+    request: Request,
+    db: AsyncSession = Depends(get_db),
+) -> User:
+    """Extract API key from header and return the authenticated user.
+
+    The API key is sent in the X-API-Key header on every request.
+    Login endpoint is excluded from this check.
+    """
+    api_key = request.headers.get("X-API-Key")
+    if not api_key:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Missing API key in X-API-Key header",
+        )
+
+    result = await db.execute(
+        select(User).where(User.api_key == api_key, User.active == True)
+    )
+    user = result.scalar_one_or_none()
+
+    if user is None:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid or inactive API key",
+        )
+
+    # Store user_id in request state for access logging middleware
+    request.state.user_id = user.id
+
+    return user
+
+
+def require_role(role: str):
+    """Dependency factory that checks if user has a specific role."""
+    async def check_role(user: User = Depends(get_current_user)) -> User:
+        if not user.has_role(role) and not user.is_admin:
+            raise HTTPException(
+                status_code=status.HTTP_403_FORBIDDEN,
+                detail=f"Role '{role}' required",
+            )
+        return user
+    return check_role
+
+
+def require_admin():
+    """Dependency that checks if user is admin."""
+    async def check_admin(user: User = Depends(get_current_user)) -> User:
+        if not user.is_admin:
+            raise HTTPException(
+                status_code=status.HTTP_403_FORBIDDEN,
+                detail="Admin access required",
+            )
+        return user
+    return check_admin
+
+
+# Pre-built role dependencies for convenience
+require_maker = require_role("Maker")
+require_measurement_tec = require_role("MeasurementTec")
+require_metrologist = require_role("Metrologist")
+require_admin_user = require_admin()