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/schemas/render_position.py

@@ -1,36 +1,3 @@
-import uuid
-from datetime import datetime
-from pydantic import BaseModel
-
-
-class RenderPositionCreate(BaseModel):
-    name: str
-    rotation_x: float = 0.0
-    rotation_y: float = 0.0
-    rotation_z: float = 0.0
-    is_default: bool = False
-    sort_order: int = 0
-
-
-class RenderPositionPatch(BaseModel):
-    name: str | None = None
-    rotation_x: float | None = None
-    rotation_y: float | None = None
-    rotation_z: float | None = None
-    is_default: bool | None = None
-    sort_order: int | None = None
-
-
-class RenderPositionOut(BaseModel):
-    id: uuid.UUID
-    product_id: uuid.UUID
-    name: str
-    rotation_x: float
-    rotation_y: float
-    rotation_z: float
-    is_default: bool
-    sort_order: int
-    created_at: datetime
-    updated_at: datetime
-
-    model_config = {"from_attributes": True}
+# Compat shim — use app.domains.rendering.schemas instead
+from app.domains.rendering.schemas import RenderPositionCreate, RenderPositionPatch, RenderPositionOut
+__all__ = ["RenderPositionCreate", "RenderPositionPatch", "RenderPositionOut"]