fix: add request timeouts to send_message_tool HTTP calls

[memosr]

_send_discord(), _send_slack(), and _send_twilio() all created aiohttp.ClientSession() without a timeout, leaving HTTP requests able to hang indefinitely. _send_whatsapp() already used aiohttp.ClientTimeout(total=30) — this fix applies the same pattern consistently to all platform send functions.

• Add ClientTimeout(total=30) to _send_discord() ClientSession
• Add ClientTimeout(total=30) to _send_slack() ClientSession
• Add ClientTimeout(total=30) to _send_twilio() ClientSession

What does this PR do?

Related Issue

Fixes #

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

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Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform:

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

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• This skill is broadly useful to most users (if bundled) — see Contributing Guide
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