refactor: migrate Feature to billing module and split ProductMedia to catalog

- Move Feature model from models/database/ to app/modules/billing/models/
  (tightly coupled to SubscriptionTier for tier-based access control)
- Move ProductMedia from models/database/media.py to app/modules/catalog/models/
  (product-specific media associations belong with catalog)
- Keep MediaFile as CORE in models/database/media.py (cross-cutting file storage)
- Convert legacy feature.py to re-export for backwards compatibility
- Update all imports to use canonical module locations

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

models/database/media.py

@@ -1,27 +1,25 @@
 # models/database/media.py
 """
-Media file models for vendor media library.
+CORE media file model for vendor media library.
 
-This module provides:
-- MediaFile: Vendor-uploaded media files (images, documents, videos)
-- ProductMedia: Many-to-many relationship between products and media
+This is a CORE framework model used across multiple modules.
+MediaFile provides vendor-uploaded media files (images, documents, videos).
+
+For product-media associations, use:
+    from app.modules.catalog.models import ProductMedia
 
 Files are stored in vendor-specific directories:
   uploads/vendors/{vendor_id}/{folder}/{filename}
 """
 
-from datetime import datetime
-
 from sqlalchemy import (
     Boolean,
     Column,
-    DateTime,
     ForeignKey,
     Index,
     Integer,
     String,
     Text,
-    UniqueConstraint,
 )
 from sqlalchemy.dialects.sqlite import JSON
 from sqlalchemy.orm import relationship
@@ -75,6 +73,7 @@ class MediaFile(Base, TimestampMixin):
 
     # Relationships
     vendor = relationship("Vendor", back_populates="media_files")
+    # ProductMedia relationship uses string reference to avoid circular import
     product_associations = relationship(
         "ProductMedia",
         back_populates="media",
@@ -122,52 +121,7 @@ class MediaFile(Base, TimestampMixin):
         return self.media_type == "document"
 
 
-class ProductMedia(Base, TimestampMixin):
-    """Association between products and media files.
+# Re-export ProductMedia from its canonical location for backwards compatibility
+from app.modules.catalog.models import ProductMedia  # noqa: E402, F401
 
-    Tracks which media files are used by which products,
-    including the usage type (main image, gallery, variant, etc.)
-    """
-
-    __tablename__ = "product_media"
-
-    id = Column(Integer, primary_key=True, index=True)
-    product_id = Column(
-        Integer,
-        ForeignKey("products.id", ondelete="CASCADE"),
-        nullable=False,
-    )
-    media_id = Column(
-        Integer,
-        ForeignKey("media_files.id", ondelete="CASCADE"),
-        nullable=False,
-    )
-
-    # Usage type
-    usage_type = Column(String(50), nullable=False, default="gallery")
-    # Types: main_image, gallery, variant, thumbnail, swatch
-
-    # Display order for galleries
-    display_order = Column(Integer, default=0)
-
-    # Variant-specific (if usage_type is variant)
-    variant_id = Column(Integer)  # Reference to variant if applicable
-
-    # Relationships
-    product = relationship("Product")
-    media = relationship("MediaFile", back_populates="product_associations")
-
-    __table_args__ = (
-        UniqueConstraint(
-            "product_id", "media_id", "usage_type",
-            name="uq_product_media_usage"
-        ),
-        Index("idx_product_media_product", "product_id"),
-        Index("idx_product_media_media", "media_id"),
-    )
-
-    def __repr__(self):
-        return (
-            f"<ProductMedia(product_id={self.product_id}, "
-            f"media_id={self.media_id}, usage='{self.usage_type}')>"
-        )
+__all__ = ["MediaFile", "ProductMedia"]