DIAG: Add /diag/testdbwrite endpoint

FIX: Log webhook set event using ILogger and set dropPendingUpdates: true

FIX: Resolve BeginScope nullability warning in build

DIAG: Print masked token in /diag endpoint

DIAG: Add LastErrorDate to /diag endpoint

DIAG: Add InMemoryLogger and /diag/logs endpoint for C# event visibility

DIAG: Add /diag/db endpoint for real-time database state inspection

ADD: /diag endpoint to test Telegram API connectivity

FIX: Remove HTTPS redirect + add retry for photo downloads (3 attempts with backoff)

AUTO-WEBHOOK: Register Telegram webhook on startup. Bot works immediately after every rebuild.

GPU auto-registration: dynamic URL resolution from MongoDB

Clear all hardcoded secrets - read from HF Space env vars instead

Deploy app without exposed API tokens