Port to Jellyfin 12.0 (net10.0, targetAbi 12.0.0.0)

- csproj: net9.0 -> net10.0, version 2.1.0.0 -> 3.0.0.0
- Jellyfin.Controller 10.*-* -> 12.*-* with ExcludeAssets="runtime"
- drop redundant Microsoft.Extensions.Http ref (NU1510 under the .NET 10 SDK;
  IHttpClientFactory comes from the Microsoft.AspNetCore.App framework ref)
- NetAnalyzers 9.0.0 -> 10.0.100
- Endpoints: bare [Authorize] -> [Authorize(Policy = "DefaultAuthorization")]
  now that legacy authorization is disabled by default
- drop unused using in AnilistApi.cs
- build.yaml + manifest.json: 3.0.0.0 / abi 12.0.0.0 entry
- gitignore local dist/ release-artifact dir

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

build.yaml

@@ -1,15 +1,15 @@
 ---
 name: "AnilistSync"
 guid: "18c2a8ea-afa0-4a0b-aa94-072b492ab80b"
-version: "2.1.0.0"
-targetAbi: "10.11.0.0"
+version: "3.0.0.0"
+targetAbi: "12.0.0.0"
 owner: "ARufenach"
 overview: "Scrobble to Anilist"
 description: >
   Jellyfin plugin to scrobble to Anilist
 category: "General"
-framework: "net9.0"
+framework: "net10.0"
 artifacts:
 - "Jellyfin.Plugin.AnilistSync.dll"
 changelog: >
-  Added support for Jellyfin 10.11 (migrated IServerEntryPoint to IHostedService, net9.0)
+  Ported to Jellyfin 12.0 (net10.0, targetAbi 12.0.0.0). Switched plugin API controller to the DefaultAuthorization policy.