refactor: delete unreachable members and redundant package refs

Eight public members had no caller anywhere in src: GitService.GetFileDiffAsync,
SubtaskRepository.DeleteByTaskIdAsync, TaskRepository.GetByListAsync (a
backwards-compat alias for GetByListIdAsync) and .GetByCreatorAsync,
WorktreeRepository.GetByStatesAsync, TaskMonitorViewModel.SetPendingQuestion
(a duplicate of the live-event lambda), PrimeClaudeTabViewModel.ApplyFiredEvent,
and StreamLineFormatter.FormatFile. TaskAttachmentRepository.DeleteAllForTaskAsync
was reachable only from its own test; the ON DELETE CASCADE on task_attachments
already covers it. Tests for the deleted members go with them.

Dropped two package refs the platform already provides: EntityFrameworkCore.Design
in Worker (the design-time factory and the migrations live in Data, which has its
own ref) and System.IO.FileSystem.AccessControl in Installer.Tests (net8.0-windows
ships the ACL APIs in the shared framework).

src/ClaudeDo.Data/Git/GitService.cs

@@ -215,15 +215,6 @@ public sealed class GitService
         args.AddRange(paths);
     }
 
-    public async Task<string> GetFileDiffAsync(string worktreePath, string? baseCommit, string relativePath, CancellationToken ct = default)
-    {
-        string[] args = string.IsNullOrEmpty(baseCommit)
-            ? ["diff", "--", relativePath]
-            : ["diff", $"{baseCommit}..HEAD", "--", relativePath];
-        var (_, stdout, _) = await RunGitAsync(worktreePath, args, ct);
-        return stdout;
-    }
-
     public async Task WorktreeRemoveAsync(string repoDir, string worktreePath, bool force = false, CancellationToken ct = default)
     {
         var args = new List<string> { "worktree", "remove" };