feat(data,worker): add repositories, stale-task recovery, and test foundation

Data: TagRepository, ListRepository, TaskRepository (incl. queue selection via
effective agent tag + scheduled_for filter), WorktreeRepository. All CRUD via
parameterized SqliteCommand; enums roundtrip as lowercase strings matching the
schema CHECK constraints.

Worker: StaleTaskRecovery IHostedService flips running -> failed on startup and
marks the result column with a [stale] reason. All four repositories registered
as singletons.

Tests: DbFixture with temp-file SQLite + schema bootstrap, covering
TaskRepository (queue pick via list-tag and task-tag, schedule filter,
transitions, stale flip), ListRepository CRUD + junctions, and
StaleTaskRecovery. 14 tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Worker/Services/StaleTaskRecovery.cs

@@ -0,0 +1,26 @@
+using ClaudeDo.Data.Repositories;
+
+namespace ClaudeDo.Worker.Services;
+
+public sealed class StaleTaskRecovery : IHostedService
+{
+    private readonly TaskRepository _tasks;
+    private readonly ILogger<StaleTaskRecovery> _logger;
+
+    public StaleTaskRecovery(TaskRepository tasks, ILogger<StaleTaskRecovery> logger)
+    {
+        _tasks = tasks;
+        _logger = logger;
+    }
+
+    public async Task StartAsync(CancellationToken cancellationToken)
+    {
+        var flipped = await _tasks.FlipAllRunningToFailedAsync("worker restart", cancellationToken);
+        if (flipped > 0)
+            _logger.LogWarning("Stale task recovery: flipped {Count} running task(s) to failed", flipped);
+        else
+            _logger.LogInformation("Stale task recovery: no stale tasks found");
+    }
+
+    public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+}