Add authors pages and requestType notifications

Introduce full authors browsing/detail feature and enhance notifications to support type-specific titles.

- Add server APIs: authors search, author detail, and author books routes (audnexus integration) that require auth and enrich results with library matches.
- Add frontend pages/components: /authors listing and /authors/[asin] detail pages; AuthorCard, AuthorGrid, AuthorDetailCard, SimilarAuthorsRow, and related skeletons.
- Add hook and integration stubs: new useAuthors hook and audnexus-authors integration; update audible service to expose audibleBaseUrl.
- Update AudiobookDetailsModal to use audibleBaseUrl and link author names to author detail pages.
- Add header navigation link to Authors.
- Notifications: extend docs and code to include requestType (audiobook|ebook), add getEventTitle/getEventMeta helpers, update queue signature and providers/processors/tests to pass/handle requestType so titles can be resolved per request type.
- Misc: job queue, processors, provider tests and notification tests updated to reflect new behavior.

This change enables browsing authors and provides type-aware notification titles without per-provider changes.

src/lib/integrations/audnexus-authors.ts

@@ -0,0 +1,104 @@
+/**
+ * Component: Audnexus Author API Integration
+ * Documentation: documentation/integrations/audible.md
+ *
+ * Shared utilities for fetching author data from the Audnexus API.
+ * Used by author search, author detail, and similar authors routes.
+ */
+
+import axios from 'axios';
+import { RMABLogger } from '@/lib/utils/logger';
+
+const logger = RMABLogger.create('Audnexus.Authors');
+
+const AUDNEXUS_BASE = 'https://api.audnex.us';
+const AUDNEXUS_TIMEOUT = 10000;
+const AUDNEXUS_HEADERS = { 'User-Agent': 'ReadMeABook/1.0' };
+
+export interface AudnexusAuthorSearch {
+  asin: string;
+  name: string;
+}
+
+export interface AudnexusAuthorGenre {
+  asin: string;
+  name: string;
+  type: string;
+}
+
+export interface AudnexusAuthorSimilar {
+  asin: string;
+  name: string;
+}
+
+export interface AudnexusAuthorDetail {
+  asin: string;
+  name: string;
+  description?: string;
+  image?: string;
+  region: string;
+  genres?: AudnexusAuthorGenre[];
+  similar?: AudnexusAuthorSimilar[];
+}
+
+/**
+ * Fetch with retry and exponential backoff for Audnexus API
+ */
+export async function audnexusFetchWithRetry(url: string, params: Record<string, string>, maxRetries = 3): Promise<any> {
+  let lastError: Error | null = null;
+
+  for (let attempt = 0; attempt <= maxRetries; attempt++) {
+    try {
+      return await axios.get(url, {
+        params,
+        timeout: AUDNEXUS_TIMEOUT,
+        headers: AUDNEXUS_HEADERS,
+      });
+    } catch (error: any) {
+      lastError = error;
+      const status = error.response?.status;
+      const isRetryable = !status || status === 503 || status === 429 || status >= 500;
+
+      if (!isRetryable) throw error;
+      if (attempt === maxRetries) break;
+
+      const backoffMs = Math.pow(2, attempt) * 1000;
+      logger.info(`Audnexus request failed (${status || 'network error'}), retrying in ${backoffMs}ms (attempt ${attempt + 1}/${maxRetries})`);
+      await new Promise(resolve => setTimeout(resolve, backoffMs));
+    }
+  }
+
+  throw lastError || new Error('Audnexus request failed after retries');
+}
+
+/**
+ * Search authors via Audnexus and return deduplicated results
+ */
+export async function searchAuthors(name: string, region: string): Promise<AudnexusAuthorSearch[]> {
+  const response = await audnexusFetchWithRetry(`${AUDNEXUS_BASE}/authors`, { region, name });
+  const results: AudnexusAuthorSearch[] = response.data;
+
+  const seen = new Set<string>();
+  return results.filter(author => {
+    if (seen.has(author.asin)) return false;
+    seen.add(author.asin);
+    return true;
+  });
+}
+
+/**
+ * Fetch full author details from Audnexus
+ */
+export async function fetchAuthorDetail(asin: string, region: string): Promise<AudnexusAuthorDetail | null> {
+  try {
+    const response = await audnexusFetchWithRetry(`${AUDNEXUS_BASE}/authors/${asin}`, { region });
+    return response.data;
+  } catch (error: any) {
+    if (error.response?.status === 404) {
+      logger.debug(`Author not found on Audnexus: ${asin}`);
+    } else {
+      logger.warn(`Failed to fetch author detail: ${asin}`, { error: error.message });
+    }
+    return null;
+  }
+}