Implement Firebase deploy target

[Photon101]

Summary

• replace the Firebase target placeholder with a deploy plan artifact that records the resolved Firebase CLI command
• support Firebase CLI options for project id, deploy target filters, config path, and release message
• execute real deployments through firebase-tools with FIREBASE_TOKEN from the sh1pt vault while keeping dry-run side-effect free

Validation

• corepack pnpm exec vitest run packages/targets/deploy-firebase/src/index.test.ts
• corepack pnpm --filter @profullstack/sh1pt-target-deploy-firebase build
• git diff --check

I also checked open PRs for Firebase/deploy-firebase duplicates before opening this.