Walkthrough: Telegram Premium Sync Fix (PRO)

This document explains the final, production-ready fix for the Telegram Premium Sync between the HollowScan Mobile App and the @HollowScanBot.

1. Technical Changes in app.py

What: I replaced isoformat() (which often includes +00:00 or Z) with datetime.now(timezone.utc).replace(tzinfo=None).isoformat().
Why: The Telegram bot's database (bot_users.json) uses "naive" ISO strings without timezone offsets. If the offset is present, the bot's comparison expiry_dt > now fails, causing the bot to think you are "Not Subscribed."
Benefit: Absolute compatibility with the bot's existing logic.

What: I updated the dictionary update logic from bot_users[tid] = { "expiry": ... } to bot_users[tid] = { **bot_users.get(tid, {}), "expiry": ... }.
Why: The old code would have wiped out the user's Telegram username or their alert filter categories when updating their premium status.
Benefit: No data loss. The user's bot settings remain perfectly intact.

What: The backend now passes the actual payment source ("google", "apple", or "mobile_app") to the bot's data file.
Why: You mentioned that a user could pay via Apple Pay or Google Play. Using a hardcoded "source": "google_play" for everyone was misleading.
Benefit: Better analytics in the bot's dashboard and status messages.

What: I added logic to the /v1/user/telegram/link endpoint to check if the app user is already premium.
Why: Previously, syncing only happened from the Bot -> App. Now, if a subscriber links their Telegram, the App -> Bot sync triggers immediately.
Benefit: 100% bi-directional sync. It works perfectly whether you pay in the app or the bot.

Background Tasks: The bot-syncing logic runs via background_tasks.add_task(...). This means even if the Supabase write fails or is slow, it will not slow down the app or interfere with the user's purchase verification.
Isolation: These changes are strictly within the update_bot_user_premium and sync_google_premium_to_telegram functions. They do not modify your main SQL tables (users, messages, etc.) or the authentication flow.
Error Handling: Every bot-sync operation is wrapped in a try...except block. If anything goes wrong, it logs a clear error to your Railway dashboard but never crashes the app.