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/services/measurement_service.py

@@ -0,0 +1,77 @@
+"""Measurement service - pass/fail calculation, data storage."""
+from decimal import Decimal
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from models.measurement import Measurement
+from models.task import RecipeSubtask
+
+
+def calculate_pass_fail(
+    value: float, subtask: RecipeSubtask
+) -> tuple[str, float | None]:
+    """Calculate pass/fail status and deviation based on tolerances.
+
+    Returns (status, deviation) where status is 'pass', 'warning', or 'fail'.
+
+    Logic:
+    - If value is outside UTL/LTL -> 'fail'
+    - If value is outside UWL/LWL but inside UTL/LTL -> 'warning'
+    - Otherwise -> 'pass'
+    """
+    deviation = None
+    if subtask.nominal is not None:
+        deviation = float(Decimal(str(value)) - Decimal(str(subtask.nominal)))
+
+    # Check fail (outside tolerance limits)
+    if subtask.utl is not None and value > float(subtask.utl):
+        return "fail", deviation
+    if subtask.ltl is not None and value < float(subtask.ltl):
+        return "fail", deviation
+
+    # Check warning (outside warning limits)
+    if subtask.uwl is not None and value > float(subtask.uwl):
+        return "warning", deviation
+    if subtask.lwl is not None and value < float(subtask.lwl):
+        return "warning", deviation
+
+    return "pass", deviation
+
+
+async def save_measurement(
+    db: AsyncSession,
+    subtask_id: int,
+    version_id: int,
+    measured_by: int,
+    value: float,
+    lot_number: str | None = None,
+    serial_number: str | None = None,
+    input_method: str = "manual",
+) -> Measurement:
+    """Save a single measurement with auto-calculated pass/fail."""
+    # Get subtask for tolerance values
+    result = await db.execute(
+        select(RecipeSubtask).where(RecipeSubtask.id == subtask_id)
+    )
+    subtask = result.scalar_one_or_none()
+    if subtask is None:
+        raise ValueError(f"Subtask {subtask_id} not found")
+
+    pass_fail, deviation = calculate_pass_fail(value, subtask)
+
+    measurement = Measurement(
+        subtask_id=subtask_id,
+        version_id=version_id,
+        measured_by=measured_by,
+        value=value,
+        pass_fail=pass_fail,
+        deviation=deviation,
+        lot_number=lot_number,
+        serial_number=serial_number,
+        input_method=input_method,
+    )
+    db.add(measurement)
+    await db.flush()
+    await db.refresh(measurement)
+    return measurement