Add migration to seed default dropdown options

Populates the dropdown_options table with default channels,
sub-channels, and proof types that were previously hardcoded:
- Social (Meta, X, LinkedIn, TikTok, YouTube)
- Display (Programmatic, Direct Buy, Rich Media)
- Email (Marketing, Transactional)
- Print (Magazine, Newspaper, Direct Mail)
- OOH (Billboard, Transit, Street Furniture)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/alembic/versions/002_seed_dropdown_options.py

@@ -0,0 +1,94 @@
+"""Seed default dropdown options
+
+Revision ID: 002_seed_dropdown
+Revises: 001_initial
+Create Date: 2024-12-18
+
+"""
+from typing import Sequence, Union
+from uuid import uuid4
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+# revision identifiers, used by Alembic.
+revision: str = '002_seed_dropdown'
+down_revision: Union[str, None] = '001_initial'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Seed default channel/sub-channel/proof-type options."""
+
+    # Default dropdown hierarchy (from original hardcoded values)
+    dropdown_data = {
+        "Social": {
+            "Meta": ["In-feed 1x1", "In-feed 4x5", "In-feed 9x16", "Stories"],
+            "X (Twitter)": ["In-feed 1x1", "In-feed 16x9"],
+            "LinkedIn": ["In-feed 1x1", "In-feed 1.91x1"],
+            "TikTok": ["In-feed 9x16"],
+            "YouTube": ["Pre-roll", "Bumper", "Display"],
+        },
+        "Display": {
+            "Programmatic": ["300x250", "300x600", "728x90", "160x600", "320x50"],
+            "Direct Buy": ["300x250", "300x600", "728x90", "970x250"],
+            "Rich Media": ["Expandable", "Interstitial", "Floating"],
+        },
+        "Email": {
+            "Marketing": ["Newsletter", "Promotional", "Product Update"],
+            "Transactional": ["Confirmation", "Receipt", "Notification"],
+        },
+        "Print": {
+            "Magazine": ["Full Page", "Half Page", "Quarter Page"],
+            "Newspaper": ["Full Page", "Half Page", "Quarter Page"],
+            "Direct Mail": ["Letter", "Postcard", "Brochure"],
+        },
+        "OOH": {
+            "Billboard": ["Standard", "Digital", "Spectacular"],
+            "Transit": ["Bus Shelter", "Rail", "Airport"],
+            "Street Furniture": ["Kiosk", "Bench", "Phone Box"],
+        },
+    }
+
+    # Get connection for raw SQL inserts
+    conn = op.get_bind()
+
+    for channel_name, sub_channels in dropdown_data.items():
+        # Insert channel
+        channel_id = str(uuid4())
+        conn.execute(
+            sa.text("""
+                INSERT INTO dropdown_options (id, option_type, parent_id, value, display_order)
+                VALUES (:id, 'channel', NULL, :value, 0)
+            """),
+            {"id": channel_id, "value": channel_name}
+        )
+
+        for sub_channel_name, proof_types in sub_channels.items():
+            # Insert sub-channel
+            sub_channel_id = str(uuid4())
+            conn.execute(
+                sa.text("""
+                    INSERT INTO dropdown_options (id, option_type, parent_id, value, display_order)
+                    VALUES (:id, 'sub_channel', :parent_id, :value, 0)
+                """),
+                {"id": sub_channel_id, "parent_id": channel_id, "value": sub_channel_name}
+            )
+
+            for proof_type_name in proof_types:
+                # Insert proof type
+                proof_type_id = str(uuid4())
+                conn.execute(
+                    sa.text("""
+                        INSERT INTO dropdown_options (id, option_type, parent_id, value, display_order)
+                        VALUES (:id, 'proof_type', :parent_id, :value, 0)
+                    """),
+                    {"id": proof_type_id, "parent_id": sub_channel_id, "value": proof_type_name}
+                )
+
+
+def downgrade() -> None:
+    """Remove all seeded dropdown options."""
+    op.execute("DELETE FROM dropdown_options WHERE option_type IN ('channel', 'sub_channel', 'proof_type')")