feat(nfo): implement NFO diagnostics and repair

- Add NFO API endpoints: diagnostics, repair, validate, needs-repair
- Create /settings/nfo page with full NFO management UI
- Add NFO status section to edit modal with repair functionality
- Add anime details API for edit modal pre-fill data
- Fix auth test fixtures in test_nfo_diagnostics_repair.py

Implements NFO diagnostics when editing anime series via right-click menu.
Users can now check NFO status, see missing tags, and repair NFOs
directly from the edit modal or the dedicated NFO settings page.

src/server/web/static/css/components/modals.css

@@ -469,4 +469,101 @@
   flex-shrink: 0;
 }
 
+/* Series Info Grid (Read-only display) */
+.info-grid {
+  display: grid;
+  grid-template-columns: repeat(2, 1fr);
+  gap: var(--spacing-sm) var(--spacing-lg);
+}
+
+.info-item {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+}
+
+.info-item label {
+  font-size: var(--font-size-caption);
+  color: var(--color-text-secondary);
+  font-weight: 500;
+}
+
+.info-item .info-value {
+  font-size: var(--font-size-body);
+  color: var(--color-text-primary);
+}
+
+/* Input with action button */
+.input-with-action {
+  display: flex;
+  gap: var(--spacing-sm);
+  align-items: center;
+}
+
+.input-with-action .input-field {
+  flex: 1;
+}
+
+.btn-fetch-tmdb {
+  flex-shrink: 0;
+  white-space: nowrap;
+}
+
+/* TMDB Search Results */
+.tmdb-search-results {
+  margin-top: var(--spacing-sm);
+  border: 1px solid var(--color-border);
+  border-radius: var(--border-radius);
+  background: var(--color-surface);
+  max-height: 200px;
+  overflow-y: auto;
+}
+
+.tmdb-result-item {
+  padding: var(--spacing-sm) var(--spacing-md);
+  cursor: pointer;
+  border-bottom: 1px solid var(--color-divider);
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+}
+
+.tmdb-result-item:last-child {
+  border-bottom: none;
+}
+
+.tmdb-result-item:hover {
+  background: var(--color-background-subtle);
+}
+
+.tmdb-result-title {
+  font-weight: 500;
+  color: var(--color-text-primary);
+}
+
+.tmdb-result-overview {
+  font-size: var(--font-size-caption);
+  color: var(--color-text-secondary);
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.tmdb-error,
+.tmdb-no-results,
+.tmdb-selected {
+  padding: var(--spacing-sm) var(--spacing-md);
+  font-size: var(--font-size-caption);
+  color: var(--color-text-secondary);
+  margin: 0;
+}
+
+.tmdb-error {
+  color: var(--color-error, #e74c3c);
+}
+
+.tmdb-selected {
+  color: var(--color-success, #2ecc71);
+}
+