fix(gateway): harden malformed env port overrides

[Frowtek]

What does this PR do?

This PR fixes a gateway config parsing bug where malformed environment values for BLUEBUBBLES_WEBHOOK_PORT or WECOM_CALLBACK_PORT could crash _apply_env_overrides() with a ValueError.

gateway/config.py already has _coerce_int() for defensive numeric parsing, but these two env override paths were still using raw int(...). This change switches them to _coerce_int(..., 8645) so invalid values fall back to the documented default port instead of crashing gateway startup or config loading.

Related Issue

No linked issue; found via code inspection.

Type of Change

• 🐛 Bug fix

Changes Made

• Updated gateway/config.py to use _coerce_int() for WECOM_CALLBACK_PORT and BLUEBUBBLES_WEBHOOK_PORT
• Added regression tests in tests/gateway/test_config.py covering malformed env values for both ports

How to Test

1. Before the fix, set either:

   • BLUEBUBBLES_SERVER_URL=http://localhost:1234
   • BLUEBUBBLES_PASSWORD=secret
   • BLUEBUBBLES_WEBHOOK_PORT=not-a-port

   or:

   • WECOM_CALLBACK_CORP_ID=corp-id
   • WECOM_CALLBACK_CORP_SECRET=corp-secret
   • WECOM_CALLBACK_PORT=not-a-port

2. Call _apply_env_overrides(GatewayConfig()) or load gateway config. Before the fix, it raises ValueError. After the fix, it falls back to 8645.

3. Run:

   • pytest tests/gateway/test_config.py -k MalformedEnvPortOverrides -q
   • pytest tests/gateway/test_config.py -q

Checklist

• test added
• tests passing
• cross-platform behavior considered
• only relevant changes included

[teknium1]

Thanks for identifying this malformed-environment startup failure mode. The requested behavior is already present on current main.

• gateway/config.py:1918 and gateway/config.py:1974 now use getenv_int(..., 8645) for the two ports.
• gateway/config.py:192-199 catches malformed integer values and returns the default instead of raising.
• Commit a7dd98c8609c0d944e3c5dd0c5b9ee31dd99eb29 implemented this as part of the broader malformed numeric environment-variable hardening; it is contained in release v2026.7.1.
• The linked duplicate discussion on fix(config): guard WECOM_CALLBACK_PORT/BLUEBUBBLES_WEBHOOK_PORT against malformed env var #48748 also records that this bug class was superseded by the canonical fix.

Automated hermes-sweeper review.