fix(bot): self-exit on sustained getUpdates network outage

[Time4Mind]

Problem

The bot's _error_handler exits the process on a sustained Conflict storm (a second poller owns the token — unrecoverable by retry) so the supervisor converges on one clean instance. But the network-error branch had no such escape hatch: on NetworkError/TimedOut it logged a single debounced one-liner and returned, trusting PTB's polling to self-recover.

In production that trust broke. A night-time proxy/VPN outage left the long-poll getUpdates wedged on a half-open socket. The bot stayed running but deaf — it never recovered even after the upstream came back, and sat silent for ~6h until a manual restart. The container's restart: unless-stopped couldn't help because the process never exited.

Fix

Add the symmetric self-heal for sustained network outages: if NetworkError/TimedOut persist contiguously longer than NETWORK_MAX_SECONDS (180s), log CRITICAL and exit non-zero via the existing _terminate_for_sustained_conflict() seam. The supervisor then respawns a clean instance that opens a fresh getUpdates connection.

Contiguity is judged by NETWORK_GAP_SECONDS (45s): a quiet gap longer than that proves a poll succeeded in between (recovery), so the outage clock resets. This means sporadic blips on a healthy idle bot never accumulate toward the threshold — only a genuinely stuck poll trips it.

Composes with both supervisors:

• Docker (restart: unless-stopped) → respawns the container.
• ccbot-supervisor.sh → os._exit(1) is EXIT_CRASH, and its wait-for-net loop gates the restart, so a still-down network can't cause a restart storm.

Tests

3 new cases in test_conflict_exit.py:

• a single network blip is tolerated (no exit),
• a contiguous outage past the budget exits exactly once,
• a quiet gap resets the outage clock so spread-out blips never trip it.

Full suite green (732 passed locally + in an ephemeral docker build of this branch). app.py untouched since #111, so this applies cleanly on current main.

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