fix(telegram): require getUpdates progress before polling is healthy

[kshitijk4poor]

Summary

Salvage of #63581 (CI blocked for first-time contributor). Makes Telegram polling health depend on successful getUpdates progress rather than get_me() return. PTB's Updater.start_polling() can return after creating its retry task but before the first getUpdates request succeeds — a cold start or reconnect could log "Connected", clear degraded send protection, and remain alive-but-deaf indefinitely.

Changes

• Instruments only the dedicated PTB get_updates_request (general Bot API calls cannot mark polling healthy).
• Binds every polling start to an immutable generation inherited by PTB child tasks, so late requests from old pollers cannot affect their replacement.
• Routes cold start, network recovery, and conflict recovery through one bounded start primitive + one owned progress verifier.
• Keeps outbound delivery fail-closed while polling is degraded; only matching-generation HTTP 2xx getUpdates progress clears it and resets counters.
• Fences teardown before recovery can re-arm; cancels and awaits recovery/verifier owners.
• Restores correct health/mode transitions for sequential same-adapter webhook reconnects.
• Preserves persistent 409 retry escalation after start_polling() returns; resets counter only after real polling progress.

Attribution

Cherry-picked from @arnispiekus's #63581 with authorship preserved. Built on top of #63247 (SilentKnight87) which was merged via #64368.

Validation

• 22 passed in test_telegram_polling_progress.py
• 7 passed in test_telegram_polling_progress_ptb.py (PTB integration, real request objects)
• 51 passed in test_telegram_network_reconnect.py
• 15 passed in test_telegram_conflict.py
• 9 passed in test_telegram_send_path_health.py
• ruff + py_compile clean
• Note: PTB tests must run in separate processes (subprocess-per-file isolation) — cross-file mock leakage causes failures when run in the same process. CI runs them separately.

AUTHOR_MAP

Added arnispiekus mapping in a separate chore commit (required for check-attribution).