refactor(B1): migrate to domain-driven project structure

Move all models/schemas/services/routers into app/domains/.
Keep backward-compat shims in old locations for imports.
Preserves domains/rendering/tasks.py from Phase A.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/domains/products/models.py

@@ -0,0 +1,97 @@
+import uuid
+import enum
+from datetime import datetime
+from sqlalchemy import String, DateTime, Boolean, Text, ForeignKey, BigInteger, Enum as SAEnum
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+from sqlalchemy.dialects.postgresql import UUID, JSONB
+from app.database import Base
+
+
+class ProcessingStatus(str, enum.Enum):
+    pending = "pending"
+    processing = "processing"
+    completed = "completed"
+    failed = "failed"
+
+
+class CadFile(Base):
+    __tablename__ = "cad_files"
+
+    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    original_name: Mapped[str] = mapped_column(String(500), nullable=False)
+    stored_path: Mapped[str] = mapped_column(String(1000), nullable=False)
+    file_hash: Mapped[str] = mapped_column(String(64), unique=True, nullable=False, index=True)
+    file_size: Mapped[int] = mapped_column(BigInteger, nullable=True)
+    parsed_objects: Mapped[dict] = mapped_column(JSONB, nullable=True)
+    thumbnail_path: Mapped[str] = mapped_column(String(1000), nullable=True)
+    gltf_path: Mapped[str] = mapped_column(String(1000), nullable=True)
+    processing_status: Mapped[ProcessingStatus] = mapped_column(
+        SAEnum(ProcessingStatus), default=ProcessingStatus.pending, nullable=False
+    )
+    error_message: Mapped[str] = mapped_column(String(2000), nullable=True)
+    render_log: Mapped[dict] = mapped_column(JSONB, nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow, nullable=False)
+    updated_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False)
+
+    order_items: Mapped[list["OrderItem"]] = relationship("OrderItem", back_populates="cad_file")
+    products: Mapped[list["Product"]] = relationship("Product", back_populates="cad_file")
+
+
+class Product(Base):
+    __tablename__ = "products"
+
+    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    pim_id: Mapped[str] = mapped_column(String(500), nullable=False)
+    name: Mapped[str | None] = mapped_column(String(500), nullable=True)
+    category_key: Mapped[str | None] = mapped_column(String(100), nullable=True, index=True)
+    ebene1: Mapped[str | None] = mapped_column(String(500), nullable=True)
+    ebene2: Mapped[str | None] = mapped_column(String(500), nullable=True)
+    baureihe: Mapped[str | None] = mapped_column(String(500), nullable=True)
+    produkt_baureihe: Mapped[str | None] = mapped_column(String(500), nullable=True)
+    lagertyp: Mapped[str | None] = mapped_column(String(500), nullable=True)
+    name_cad_modell: Mapped[str | None] = mapped_column(String(500), nullable=True, index=True)
+    gewuenschte_bildnummer: Mapped[str | None] = mapped_column(String(500), nullable=True)
+    medias_rendering: Mapped[bool | None] = mapped_column(Boolean, nullable=True)
+    components: Mapped[list] = mapped_column(JSONB, nullable=False, default=list)
+    cad_part_materials: Mapped[list] = mapped_column(JSONB, nullable=False, default=list)
+    cad_file_id: Mapped[uuid.UUID | None] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("cad_files.id", ondelete="SET NULL"), nullable=True
+    )
+    notes: Mapped[str | None] = mapped_column(Text, nullable=True)
+    is_active: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True)
+    arbeitspaket: Mapped[str | None] = mapped_column(String(500), nullable=True)
+    source_excel: Mapped[str | None] = mapped_column(String(1000), nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow, nullable=False)
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False
+    )
+
+    cad_file: Mapped["CadFile | None"] = relationship("CadFile", back_populates="products")
+    order_lines: Mapped[list["OrderLine"]] = relationship(
+        "OrderLine", back_populates="product", cascade="all, delete-orphan"
+    )
+    render_positions: Mapped[list["ProductRenderPosition"]] = relationship(
+        "ProductRenderPosition", back_populates="product",
+        cascade="all, delete-orphan", order_by="ProductRenderPosition.sort_order"
+    )
+
+    @property
+    def thumbnail_url(self) -> str | None:
+        if self.cad_file and self.cad_file.thumbnail_path:
+            from pathlib import Path
+            return f"/thumbnails/{Path(self.cad_file.thumbnail_path).name}"
+        return None
+
+    @property
+    def processing_status(self) -> str | None:
+        if self.cad_file:
+            return self.cad_file.processing_status.value if hasattr(
+                self.cad_file.processing_status, 'value'
+            ) else str(self.cad_file.processing_status)
+        return None
+
+    @property
+    def cad_parsed_objects(self) -> list[str] | None:
+        if self.cad_file and self.cad_file.parsed_objects:
+            return self.cad_file.parsed_objects.get("objects") or []
+        return None