GracePlugin

### New Features

#### Admin GUI Panels

- Added `/grace gui` to open a full admin control panel.

- Added a timer control panel for start, pause/resume, stop, extend, reduce, and reload actions.

- Added a global flag panel with live click-to-toggle controls.

### Bug Fixes

#### Deathban Bypass

- Fixed deathban bypass handling so the bypass permission is respected when enabled.

#### Warning Intervals

- Fixed warning interval behavior so warnings trigger on threshold crossing instead of firing early in batches.

- Improved warning state tracking after time changes.

#### Pause and Resume

- Fixed pause behavior to stop only the timer task without destroying the boss bar.

- Fixed resume behavior to correctly continue countdown state and warnings.

#### Per-Player Grace Rejoin Abuse

- Fixed personal grace rejoin abuse by persisting completed personal grace records.

- Players who finish personal grace no longer receive a fresh timer on reconnect.

#### Reload and Defaults

- Fixed reload flow to refresh default flag baselines before rebuilding world/global runtime values.

#### Auto-Start and World Duration

- Fixed auto-start so it starts once instead of repeatedly restarting per enabled world.

- Fixed grace start duration resolution to use world duration defaults when no manual duration is provided.

#### Command Blocking

- Fixed blocked command matching to normalize namespaced command forms.