fix: harden BlueBubbles webhook handling

[Oceanswave]

Summary

• tolerate BlueBubbles webhook port conflicts for one-shot outbound sends by falling back to outbound-only mode
• keep outbound-only cleanup from unregistering the long-running gateway webhook
• classify status-only updated-message webhooks and dedupe inbound message payloads to avoid duplicate replies
• preserve paragraph breaks in one iMessage bubble instead of splitting normal replies into multiple bubbles

Test Plan

• python -m pytest tests/gateway/test_bluebubbles.py -q
• python -m py_compile gateway/platforms/bluebubbles.py tests/gateway/test_bluebubbles.py
• git diff --cached --check
• local smoke: patched BlueBubbles adapter connected while the gateway owned the webhook port and sent a Markdown document attachment successfully

[alt-glitch]

Related to #12439 (webhook port conflict in standalone send path) and #18395 (webhook dedup). This PR bundles fixes for multiple BlueBubbles issues: port conflict fallback, webhook lifecycle, message dedup, and paragraph handling.

[Oceanswave]

Reapplied on top of current upstream main after the Kanban DB hardening landed. Added the BlueBubbles webhook hardening plus DM chat-variant dedupe.\n\nValidation: python -m pytest tests/gateway/test_bluebubbles.py -o addopts= -q → 61 passed.

[Oceanswave]

Closing this in favor of the consolidated BlueBubbles hardening PR: #45317

That PR folds the repeated local reapply work into one clean branch and explicitly documents the purpose/struggles: BlueBubbles updates can produce duplicate inbound iMessage turns, status-only updated-message webhook echoes, fragile typing behavior, and one-shot outbound adapter conflicts with the gateway-owned webhook listener. It also includes the focused regression suite covering the consolidated behavior.

[Oceanswave]

Superseded by consolidated BlueBubbles hardening PR #45317.