Allow API users to set custom create_time, update_time, and display_time
when creating memos and comments. This enables importing historical data
with accurate timestamps.

Changes:
- Update proto definitions: change create_time and update_time from
  OUTPUT_ONLY to OPTIONAL to allow setting on creation
- Modify CreateMemo service to handle custom timestamps from request
- Update database drivers (SQLite, MySQL, PostgreSQL) to support
  inserting custom timestamps when provided
- Add comprehensive test coverage for custom timestamp functionality
- Maintain backward compatibility: auto-generated timestamps still
  work when custom values are not provided
- Fix golangci-lint issues in plugin/filter (godot and revive)

Fixes #5483