chore: Improve gifts indexing

[danoctua]

Optimize Gift Indexer Resource Allocation and Auto-Block Deleted Accounts

Description

This pull request addresses two significant stability issues within the Telegram unique gifts indexer related to background Celery workers. First, it resolves resource exhaustion (SIGKILL) caused by file descriptor leaks and event loop thrashing when polling batches of users. Second, it gracefully handles "Bad Request: user not found" exceptions by
automatically marking deleted Telegram accounts as inactive, ensuring they are excluded from future syncs.

Fixes: # (add issue number if applicable)

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

• Change 1: Refactored refresh_users_gifts_batch to execute all 25 users within a single asyncio.run() loop inside IndexerUserGiftAction, sharing a single BotApiGiftIndexer
  instance. This heavily cuts down event loop setup/teardown churn and drops SSL connection creation by 96%.
• Change 2: Added an asyncio.sleep(0.250) during indexer.close() to give aiohttp the necessary event loop tick to elegantly terminate underlying SSL connections, preventing
  OS-level file descriptor leaks leading to SIGKILL.
• Change 3: Ensured TelegramBadRequest exceptions correctly raise instead of silently continuing, preventing the indexer from falsely assuming users have lost all their gifts.
• Change 4: Intercepted "user not found" API errors across both single and batch sync tasks to automatically batch-update those users as is_blocked = True via a new UserService. mark_as_blocked method.
• Change 5: Updated UserService.get_all_telegram_ids to exclude blocked users entirely, preventing the global dispatcher from unnecessarily re-queueing deleted accounts.

How Has This Been Tested?

• Verified logic against Celery worker logs locally to ensure the indexer gracefully skips nonexistent users and correctly cascades the batch updates.
• Ensured Docker container memory limits (1024MB vs 512MB) no longer trigger OOM kills on standard operations due to the mitigated file descriptor bloat.
• Formatted and validated through pre-commit (Ruff/ESLint).

Screenshots (if applicable)

N/A

Additional Notes

The sync_user_gifts method was updated to accept an optional indexer parameter to allow the single-user priority task (Flow B) to remain unchanged while still benefiting from the
performance optimizations in the master dispatcher (Flow C).

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