Replace chapter setting with multi-select locations; add chapter character summary

Chapters now carry many Locations (new Tags-style entity with cross-referencing)
instead of a single free-text Setting field, with a Locations tab on the novel
for browsing them and seeing every chapter set at each one. Also surfaces the
distinct characters appearing in a chapter's beats, linked, under the beat/word
count on the outline tab.

src/Novelly.Api/Program.cs

@@ -10,6 +10,7 @@ using Novelly.Api.Common;
 using Novelly.Api.Data;
 using Novelly.Api.Genres;
 using Novelly.Api.Imports;
+using Novelly.Api.Locations;
 using Novelly.Api.Novels;
 using Novelly.Api.Questions;
 using Novelly.Api.Tags;
@@ -95,6 +96,7 @@ app.MapNovelEndpoints()
    .MapChapterEndpoints()
    .MapBeatEndpoints()
    .MapTagEndpoints()
+   .MapLocationEndpoints()
    .MapGenreEndpoints()
    .MapOpenQuestionEndpoints()
    .MapAgentEndpoints()