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/models/task.py

@@ -0,0 +1,76 @@
+"""RecipeTask and RecipeSubtask models."""
+from typing import TYPE_CHECKING, Optional
+
+from sqlalchemy import (
+    DECIMAL, Enum, ForeignKey, Index, Integer, JSON, String, Text, UniqueConstraint,
+)
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from database import Base
+
+if TYPE_CHECKING:
+    from models.recipe import RecipeVersion
+
+
+class RecipeTask(Base):
+    __tablename__ = "recipe_tasks"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
+    version_id: Mapped[int] = mapped_column(
+        Integer, ForeignKey("recipe_versions.id"), nullable=False
+    )
+    order_index: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
+    title: Mapped[str] = mapped_column(String(255), nullable=False)
+    directive: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
+    description: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
+    file_path: Mapped[Optional[str]] = mapped_column(String(500), nullable=True)
+    file_type: Mapped[Optional[str]] = mapped_column(
+        Enum("image", "pdf", name="file_type_enum"), nullable=True
+    )
+    annotations_json: Mapped[Optional[dict]] = mapped_column(JSON, nullable=True)
+
+    # Relationships
+    version: Mapped["RecipeVersion"] = relationship(back_populates="tasks")
+    subtasks: Mapped[list["RecipeSubtask"]] = relationship(
+        back_populates="task", cascade="all, delete-orphan", lazy="selectin"
+    )
+
+    __table_args__ = (
+        {"mysql_engine": "InnoDB", "mysql_charset": "utf8mb4"},
+    )
+
+    def __repr__(self) -> str:
+        return f"<RecipeTask #{self.order_index} '{self.title}'>"
+
+
+class RecipeSubtask(Base):
+    __tablename__ = "recipe_subtasks"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
+    task_id: Mapped[int] = mapped_column(
+        Integer, ForeignKey("recipe_tasks.id", ondelete="CASCADE"), nullable=False
+    )
+    marker_number: Mapped[int] = mapped_column(Integer, nullable=False)
+    description: Mapped[str] = mapped_column(String(500), nullable=False)
+    measurement_type: Mapped[Optional[str]] = mapped_column(String(100), nullable=True)
+
+    # Tolerance values
+    nominal: Mapped[Optional[float]] = mapped_column(DECIMAL(12, 6), nullable=True)
+    utl: Mapped[Optional[float]] = mapped_column(DECIMAL(12, 6), nullable=True)  # Upper Tolerance Limit
+    uwl: Mapped[Optional[float]] = mapped_column(DECIMAL(12, 6), nullable=True)  # Upper Warning Limit
+    lwl: Mapped[Optional[float]] = mapped_column(DECIMAL(12, 6), nullable=True)  # Lower Warning Limit
+    ltl: Mapped[Optional[float]] = mapped_column(DECIMAL(12, 6), nullable=True)  # Lower Tolerance Limit
+
+    unit: Mapped[str] = mapped_column(String(20), nullable=False, default="mm")
+
+    # Relationships
+    task: Mapped["RecipeTask"] = relationship(back_populates="subtasks")
+
+    __table_args__ = (
+        UniqueConstraint("task_id", "marker_number", name="uq_task_marker"),
+        Index("ix_subtask_task_id", "task_id"),
+        {"mysql_engine": "InnoDB", "mysql_charset": "utf8mb4"},
+    )
+
+    def __repr__(self) -> str:
+        return f"<RecipeSubtask #{self.marker_number} '{self.description}'>"