Add soft delete + trash, keyboard-first web overhaul, move chapter tags to bottom

Adds SoftDelete/Trash across characters, chapters, locations, beats with a
purge schedule and Trash page. Reworks the web client for keyboard-driven
navigation (focus helpers, help overlay, keyboard.md doc). Moves the
ChapterPage tag editor to the bottom of the page to match CharacterDetailPage.

tests/Novelly.Api.Tests/CharacterServiceTests.cs

@@ -258,7 +258,7 @@ public class CharacterServiceTests : ServiceTestFixture
     }
 
     [Test]
-    public async Task Deleting_the_canonical_character_leaves_its_other_identities_alive()
+    public async Task Trashing_the_canonical_character_keeps_the_link_so_restoring_brings_it_back()
     {
         var kael = await Characters.CreateAsync(_novelId, new CreateCharacterRequest("Kael"));
         var stranger = await Characters.CreateAsync(_novelId, new CreateCharacterRequest("The Stranger"));
@@ -268,7 +268,13 @@ public class CharacterServiceTests : ServiceTestFixture
 
         using var verification = Db.CreateContext();
         var survivor = await verification.Characters.FirstAsync(c => c.Id == stranger.Id);
-        Assert.That(survivor.SameCharacterAsId, Is.Null);
+        var response = (await Characters.GetAsync(stranger.Id))!.ToResponse();
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(survivor.SameCharacterAsId, Is.EqualTo(kael.Id), "the pin survives so restoring Kael restores the identity link");
+            Assert.That(response.SameCharacterAsName, Is.Null, "a trashed canonical identity does not show up while it's in the trash");
+        });
     }
 
     [Test]