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/recipe.py

@@ -0,0 +1,64 @@
+"""Recipe and RecipeVersion models with immutable versioning."""
+from datetime import datetime
+from typing import TYPE_CHECKING, Optional
+
+from sqlalchemy import Boolean, DateTime, ForeignKey, Index, Integer, String, Text, UniqueConstraint, func
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from database import Base
+
+if TYPE_CHECKING:
+    from models.task import RecipeTask
+
+
+class Recipe(Base):
+    __tablename__ = "recipes"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
+    code: Mapped[str] = mapped_column(String(100), unique=True, nullable=False, index=True)
+    name: Mapped[str] = mapped_column(String(255), nullable=False)
+    description: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
+    created_by: Mapped[int] = mapped_column(Integer, ForeignKey("users.id"), nullable=False)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime, nullable=False, server_default=func.now()
+    )
+    active: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True, index=True)
+
+    # Relationships
+    versions: Mapped[list["RecipeVersion"]] = relationship(
+        back_populates="recipe", cascade="all, delete-orphan", lazy="selectin"
+    )
+
+    def __repr__(self) -> str:
+        return f"<Recipe {self.code} '{self.name}'>"
+
+
+class RecipeVersion(Base):
+    __tablename__ = "recipe_versions"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
+    recipe_id: Mapped[int] = mapped_column(Integer, ForeignKey("recipes.id"), nullable=False)
+    version_number: Mapped[int] = mapped_column(Integer, nullable=False)
+    is_current: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
+
+    # Audit
+    created_by: Mapped[int] = mapped_column(Integer, ForeignKey("users.id"), nullable=False)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime, nullable=False, server_default=func.now()
+    )
+    change_notes: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
+
+    # Relationships
+    recipe: Mapped["Recipe"] = relationship(back_populates="versions")
+    tasks: Mapped[list["RecipeTask"]] = relationship(
+        back_populates="version", cascade="all, delete-orphan", lazy="selectin"
+    )
+
+    __table_args__ = (
+        UniqueConstraint("recipe_id", "version_number", name="uq_recipe_version"),
+        Index("ix_recipe_version_current", "recipe_id", "is_current"),
+        {"mysql_engine": "InnoDB", "mysql_charset": "utf8mb4"},
+    )
+
+    def __repr__(self) -> str:
+        return f"<RecipeVersion recipe={self.recipe_id} v{self.version_number}>"