feat: Migrate gift collection from slug to ID

[danoctua]

Migrate Gift Collection Indexing from Slug to Telegram Internal ID

Description

Migrate Gift Collection and Gift Unique indexing from slug-based primary keys to integer IDs (Telegram gift IDs). This is Phase 0 of the gift indexer rewrite — the schema and codebase are updated to support integer-based lookups while the full indexer rewrite is planned separately.

Checklist

Before submitting your pull request, please ensure the following:

• I have read the contributing guidelines.
• I ran all tests and they passed successfully.
• I added/updated documentation (if applicable).
• I reviewed my own code and followed the project's code style.
• I included relevant details in the PR description or commit messages.

Changes

• Database models: Replaced GiftCollection.slug (VARCHAR PK) with GiftCollection.id (BigInteger PK). Added options (JSONB) and blockchain_address fields. Replaced collection_slug FK with collection_id FK in GiftUnique
• Alembic migration: Three-phase migration — schema changes, data migration from ID-to-name JSON mapping, and schema cleanup. Supports upgrade and downgrade.
• DTOs & Services: Updated GiftCollectionDTO, GiftUniqueDTO, GiftFilterDTO, GiftCollectionService, and GiftUniqueService to use integer IDs.
• Actions & API routes: Updated GiftUniqueAction, TelegramChatGiftCollectionAction, and API endpoint from /gifts/{collection_slug} to /gifts/{collection_id}.
• Chat eligibility logic: Fixed find_relevant_gift_items to compare collection_id instead of collection_slug.
• Indexer (temporarily disabled): Added early returns to indexer tasks, commented out Celery Beat schedule and slug-dependent indexer methods pending future rewrite.

How Has This Been Tested?

• All unit tests pass via make test.
• Verified migration correctness by seeding 109 dummy collections (with gift_unique items and telegram_chat_gift_collection rules using collection_slug) and validating all three tables were correctly mapped to integer IDs after running the migration.
• Verified both alembic upgrade and alembic downgrade work correctly.

Screenshots (if applicable)

N/A — backend-only changes.

Additional Notes

• The gift indexer is intentionally disabled in this PR. Methods that relied on the old slug schema are commented out and will be rewritten in a follow-up.

---

Thank you for contributing! 🎉