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.

src/Novelly.Api/Beats/BeatEndpoints.cs

@@ -39,6 +39,11 @@ public static class BeatEndpoints
                 (await service.AssignCharacterAsync(chapterId, request, ct))?.Select(b => b.ToResponse()).ToList().ToApiResult())
             .WithSummary("Add a character to several beats at once, leaving each beat's existing characters alone.");
 
+        chapterScoped.MapPost("/move", async (
+                Guid chapterId, MoveBeatsRequest request, BeatService service, CancellationToken ct) =>
+                (await service.MoveAsync(chapterId, request, ct))?.Select(b => b.ToResponse()).ToList().ToApiResult())
+            .WithSummary("Move one or more beats to another chapter, appending them to its end.");
+
         app.MapGet("/api/characters/{characterId:guid}/beats", async (
                 Guid characterId, BeatService service, CancellationToken ct) =>
                 (await service.ListForCharacterAsync(characterId, ct))?.Select(b => b.ToCharacterBeatResponse()).ToList().ToApiResult())