fix: prevent context canceled errors in web dashboard

Detach DB queries from HTTP request context so HTMX polling doesn't
cancel in-flight queries when the browser aborts previous XHRs. Add
indexes on login_attempts and sessions to speed up frequent dashboard
queries. Bump version to 0.17.1.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/web/web_test.go

@@ -54,6 +54,30 @@ func newSeededTestServer(t *testing.T) *Server {
 	return srv
 }
 
+func TestDbContextNotCanceled(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	req = req.WithContext(ctx)
+
+	dbCtx, dbCancel := dbContext(req)
+	defer dbCancel()
+
+	// Cancel the original request context.
+	cancel()
+
+	// The DB context should still be usable.
+	select {
+	case <-dbCtx.Done():
+		t.Fatal("dbContext should not be canceled when request context is canceled")
+	default:
+	}
+
+	// Verify the DB context has a deadline (from the timeout).
+	if _, ok := dbCtx.Deadline(); !ok {
+		t.Error("dbContext should have a deadline")
+	}
+}
+
 func TestDashboardHandler(t *testing.T) {
 	t.Run("empty store", func(t *testing.T) {
 		srv := newTestServer(t)