Harden tariff source monitoring

[chohcx]

Summary

• retry transient source fetch failures up to three times with a fresh timeout
• preserve the underlying fetch cause in failure artifacts
• update the artifact uploader to the Node 24-compatible v7 runtime
• update transitive fast-uri from 3.1.5 to 3.1.7 to clear the current high advisory

Evidence

• scheduled run 33374268453 and branch run 34072212735 both saw a Taipower transport failure while other sources passed
• local checks currently resolve all five official sources

Verification

• 16 unit tests pass, including retry success and exhaustion cases
• 6 desktop/mobile E2E tests pass
• typecheck, production build, and full npm audit pass with 0 vulnerabilities
• the tariff workflow will be dispatched again from this branch before merge

Closes #12