[codex] Advance reusable release checklist (#462)

[jjoonleo]

Advances #462

References #468

Summary

• Expanded docs/Release-Checklist.md into the central reusable release checklist for generated files, verification commands, versioning, release signing, Firebase config, signed AAB evidence, store metadata, screenshots, Play declarations, device QA, pre-launch report review, and rollout monitoring.
• Added explicit privacy policy and Play Data safety review triggers for data, permissions, account deletion, UGC, category, and declaration changes.
• Linked the release checklist from docs/Home.md and added a repo-local [Release] Create reusable app release checklist #462 plan in plans/.

Verification

• rg -n "Draft status for #462|flutter analyze|flutter test|dart run build_runner build --delete-conflicting-outputs|flutter build appbundle --release|Privacy Policy And Data Safety Triggers|Store Metadata And Screenshots|Play Console Declarations|Rollout Monitoring|Release Evidence Template" docs/Release-Checklist.md
• rg -n "Release Checklist" docs/Home.md docs/Release-Checklist.md plans/462-reusable-release-checklist-plan.md
• git diff --check -- docs/Release-Checklist.md docs/Home.md plans/462-reusable-release-checklist-plan.md

Remaining human/external tasks

• Keep [Release] Create reusable app release checklist #462 open until prerequisite issues [Release] Configure release signing ownership and secrets #450-[Release] Run Play Console pre-launch report and resolve blockers #459 settle.
• Complete or close the open prerequisites: signed AAB build, initial production versioning, Play App Signing fingerprints, Play Console developer verification/package registration, release smoke test, alarm/notification QA, account deletion QA, and Play pre-launch report.
• Reconcile this checklist against the final workflow run, artifact path, fingerprints, Play Console state, QA evidence, and pre-launch report outcome before removing the draft-status note.