Add character aliases/identity links, move-beats, keyboard help overlay

- Characters can carry aliases and be linked as the same underlying
  person (canonical SameCharacterAsId, optional reveal chapter/note),
  surfaced through the API, MCP tools, agent toolset, and web UI.
- Characters page redesigned as a filterable/sortable table (name+
  aliases, role, importance, occupation, tags) instead of a sidebar
  list, to stay usable as the cast grows.
- Beats can be moved between chapters (BeatService.MoveAsync + MCP/
  agent tool + endpoint).
- Add a keyboard-shortcuts help overlay (HelpButton/HelpOverlayContext)
  wired into the project layout.
- CLAUDE.md: require every frontend component to carry a unique id
  attribute; apply it to CharacterMultiSelect and MarkdownEditor.

tests/Novelly.Api.Tests/ServiceTestFixture.cs

@@ -63,12 +63,13 @@ public abstract class ServiceTestFixture
             Db.Context, Access, UserContext, ProjectLogs, new CreateProjectRequestValidator(), new UpdateProjectRequestValidator());
         Characters = new CharacterService(
             Db.Context, Access, Tags, CharacterLogs,
-            new CreateCharacterRequestValidator(), new UpdateCharacterRequestValidator(), new CreateRelationshipRequestValidator());
+            new CreateCharacterRequestValidator(), new UpdateCharacterRequestValidator(), new CreateRelationshipRequestValidator(),
+            new LinkCharacterIdentityRequestValidator());
         Chapters = new ChapterService(Db.Context, Access, Tags, ChapterLogs, new CreateChapterRequestValidator(), new UpdateChapterRequestValidator());
         Beats = new BeatService(
             Db.Context, Access, Tags, BeatLogs,
             new CreateBeatRequestValidator(), new UpdateBeatRequestValidator(), new ReorderBeatsRequestValidator(),
-            new AssignCharacterToBeatsRequestValidator());
+            new AssignCharacterToBeatsRequestValidator(), new MoveBeatsRequestValidator());
         Arcs = new CharacterArcService(
             Db.Context, Access, ArcLogs,
             new CreateArcStageRequestValidator(), new UpdateArcStageRequestValidator(), new ReorderArcStagesRequestValidator());