feat: add authoritative C5 installer release manifests

[justcallmekoko]

Purpose

Publish authoritative flash metadata for the C5 Wardriver browser installer.

Impact

• Derives offsets and flash parameters from Arduino's expanded esptool upload recipe, with a flash_args fallback.
• Builds a review-only installer bundle on pull requests.
• Attaches hashed installer assets only for future published stable releases; existing release behavior is unchanged.

Verification

• 10 manifest unit tests and target-registry validation passed.
• Normal firmware build passed: https://github.com/justcallmekoko/ESP32DualBandWardriver/actions/runs/30768271791
• Installer bundle build passed: https://github.com/justcallmekoko/ESP32DualBandWardriver/actions/runs/30768271794