chore: polish pass — TS strictness, CHANGELOG cleanup, E2E restore test
- Replace 5 unsafe `as string` header/query casts with proper typeof
narrowing in blobs, api-v1, versions, and documents routes
- Clean up CHANGELOG: remove 70-line Chainlink task dump from 0.12.1,
move [Unreleased] to top, consolidate entries into proper categories
- Add E2E tests for version history restore action (confirm + cancel)
- Close 6 stale PRs: 5 TipTap v3 Renovate PRs (must upgrade all 24
packages together) and PR #123 (conflicted, incomplete) (#597)