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/schemas/task.py

@@ -0,0 +1,85 @@
+"""Pydantic schemas for RecipeTask and RecipeSubtask operations."""
+from typing import Any, Optional
+
+from pydantic import BaseModel, ConfigDict, Field
+
+
+class SubtaskCreate(BaseModel):
+    """Schema for creating a subtask."""
+    marker_number: int = Field(..., ge=1)
+    description: str = Field(..., min_length=1, max_length=500)
+    measurement_type: Optional[str] = Field(None, max_length=100)
+    nominal: Optional[float] = None
+    utl: Optional[float] = None
+    uwl: Optional[float] = None
+    lwl: Optional[float] = None
+    ltl: Optional[float] = None
+    unit: str = Field("mm", max_length=20)
+
+
+class SubtaskUpdate(BaseModel):
+    """Schema for updating a subtask."""
+    description: Optional[str] = Field(None, min_length=1, max_length=500)
+    measurement_type: Optional[str] = Field(None, max_length=100)
+    nominal: Optional[float] = None
+    utl: Optional[float] = None
+    uwl: Optional[float] = None
+    lwl: Optional[float] = None
+    ltl: Optional[float] = None
+    unit: Optional[str] = Field(None, max_length=20)
+
+
+class SubtaskResponse(BaseModel):
+    """Schema for subtask response."""
+    model_config = ConfigDict(from_attributes=True)
+
+    id: int
+    task_id: int
+    marker_number: int
+    description: str
+    measurement_type: Optional[str] = None
+    nominal: Optional[float] = None
+    utl: Optional[float] = None
+    uwl: Optional[float] = None
+    lwl: Optional[float] = None
+    ltl: Optional[float] = None
+    unit: str
+
+
+class TaskCreate(BaseModel):
+    """Schema for creating a task."""
+    title: str = Field(..., min_length=1, max_length=255)
+    directive: Optional[str] = None
+    description: Optional[str] = None
+    file_type: Optional[str] = Field(None, pattern="^(image|pdf)$")
+    annotations_json: Optional[dict[str, Any]] = None
+    subtasks: list[SubtaskCreate] = []
+
+
+class TaskUpdate(BaseModel):
+    """Schema for updating a task."""
+    title: Optional[str] = Field(None, min_length=1, max_length=255)
+    directive: Optional[str] = None
+    description: Optional[str] = None
+    annotations_json: Optional[dict[str, Any]] = None
+
+
+class TaskResponse(BaseModel):
+    """Schema for task response."""
+    model_config = ConfigDict(from_attributes=True)
+
+    id: int
+    version_id: int
+    order_index: int
+    title: str
+    directive: Optional[str] = None
+    description: Optional[str] = None
+    file_path: Optional[str] = None
+    file_type: Optional[str] = None
+    annotations_json: Optional[dict[str, Any]] = None
+    subtasks: list[SubtaskResponse] = []
+
+
+class TaskReorderRequest(BaseModel):
+    """Schema for reordering tasks."""
+    task_ids: list[int] = Field(..., min_length=1)