feat(backend): Add DexScreener connector database migration

- Add Alembic migration 85 to add DEXSCREENER_CONNECTOR enum value
- Migration uses IF NOT EXISTS for safe production deployment
- Add integration test script for DexScreener API endpoints
- Verify all endpoints require JWT authentication
- Confirm migration successfully applied (DB version 85)

Story 1.1 Backend: Complete ✅
- All API endpoints functional (add, delete, test)
- Database schema synchronized
- Integration tests passing
- Ready for Story 1.2 (Frontend UI)

surfsense_backend/alembic/versions/85_add_dexscreener_connector.py

@@ -0,0 +1,42 @@
+"""add dexscreener connector enum
+
+Revision ID: 85_add_dexscreener_connector
+Revises: 84_migrate_global_llm_configs_to_auto_mode
+Create Date: 2026-01-31 17:14:00.000000
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '85'
+down_revision = '84'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    """Add DEXSCREENER_CONNECTOR to searchsourceconnectortype enum."""
+    # Add new enum value using raw SQL
+    # Note: ALTER TYPE ... ADD VALUE cannot be executed inside a transaction block
+    # Alembic handles this automatically when using op.execute()
+    op.execute(
+        "ALTER TYPE searchsourceconnectortype ADD VALUE IF NOT EXISTS 'DEXSCREENER_CONNECTOR'"
+    )
+
+
+def downgrade():
+    """
+    Downgrade is not supported for enum value removal in PostgreSQL.
+    
+    Removing enum values requires:
+    1. Removing all references to the value
+    2. Creating a new enum type without the value
+    3. Migrating all columns to use the new type
+    4. Dropping the old type
+    
+    This is complex and risky, so we don't support automatic downgrade.
+    If you need to remove this enum value, do it manually.
+    """
+    pass