- Extract `scrollToCaret` helper to deduplicate scroll logic
- Unify precise scroll behavior for both manual triggers and auto-scroll

- Use `textarea-caret` for precise cursor position calculation instead of line approximation
- Update `scrollToCursor` to scroll to the actual cursor position
- Fix Safari double-enter issue with IME in list completion

This fixes a critical data loss issue where users editing the same memo
on multiple devices would overwrite each other's changes due to aggressive
browser caching, particularly in Chromium-based browsers and PWAs.

Changes:
- Backend: Add Cache-Control headers to all API responses to prevent
  browser HTTP caching
- Frontend: Force fresh fetch from server when opening memo editor by
  invalidating React Query cache
- Frontend: Reduce memo query staleTime from 60s to 10s for better
  collaborative editing support

Fixes #5470

Fixes #5472

Move cleanup logic to store.DeleteMemo to ensure data consistency:
- Delete memo_relation records where memo is source (MemoID) or target (RelatedMemoID)
- Delete attachments linked to the memo (including S3/local files)

This prevents stale COMMENT records in memo_relation after deleting
a memo that has comments.

- Filter out COMMENT type relations, only show REFERENCE type
- When editing a memo, only show relations where current memo is the source
- Pass memoName through EditorMetadata to RelationList for filtering

Add ListMemoComments to public endpoints whitelist so unauthenticated
users can see public comments. The service layer already filters
comments by visibility (only PUBLIC for guests).

Fixes #5471

Signed-off-by: Jongho Hong <myodan@pm.me>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

- Fix linting issues and address testcontainers deprecation in store/test/containers.go
- Extract MemosStartupWaitStrategy for consistent container health checks
- Refactor migrator_test.go to use a consolidated testMigration helper, reducing duplication
- Add store/test/Dockerfile for optimized local test image builds

Reverts only the system_setting → instance_setting rename related changes from commit d326c710.
Keeps the resource → attachment rename changes intact.

- Reverts table name back to system_setting in all database drivers (MySQL, PostgreSQL, SQLite)
- Removes migration files for the system_setting rename
- Reverts LATEST.sql files to use system_setting table

This fixes an issue where the theme selector on the login screen would not update its display value after selection because the component was not re-rendering. Added local state to track the current theme. Validated that this pattern is unique to the unauthenticated context.