fix(telnyx): guard invalid signature tolerance config

[aiirvizionz]

Summary

• Normalize Telnyx signature tolerance config before using it for webhook timestamp checks.
• Keep the default 300-second replay window when config receives invalid numeric values such as Infinity, NaN, or negatives.
• Add a regression test showing an old but correctly signed Telnyx webhook is rejected when the configured tolerance is invalid.

Validation

• git diff --check
• node node_modules\vitest\vitest.mjs run packages/bots/telnyx/src/index.test.ts (8 tests passed)

I also attempted pnpm vitest run packages/bots/telnyx/src/index.test.ts and pnpm --filter @profullstack/sh1pt-bot-telnyx typecheck, but this checkout stops during dependency preparation because the committed lockfile fails the active supply-chain policy: @profullstack/autoblog@0.4.0 has no tarball integrity field. I did not modify the lockfile.

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