perf(preload): bounded concurrency + drop redundant SW data cache

Fetch preload files with 6 workers in flight instead of one-at-a-time,
preserving retry/404/circuit-breaker/IDB-write-failure semantics. Browsers
already cap ~6 connections per origin, so this is safe and cuts a full
3431-file preload to roughly 1/5 the wall-clock time.

Remove the StaleWhileRevalidate routes for /data/*.json and /data/*.text.
IndexedDB is the canonical offline store (every data read falls back to it),
so the SW data caches only thrashed (200 entries over 3431 files) and added a
caches.match/cache.put to every request. Keep NetworkFirst for the manifest
and CacheFirst for fonts.

vite.config.ts

@@ -24,22 +24,6 @@ export default defineConfig({
               networkTimeoutSeconds: 3,
             },
           },
-          {
-            urlPattern: /\/data\/.*\.json$/,
-            handler: 'StaleWhileRevalidate',
-            options: {
-              cacheName: 'ponomar-data',
-              expiration: { maxEntries: 200, maxAgeSeconds: 60 * 60 * 24 * 30 },
-            },
-          },
-          {
-            urlPattern: /\/data\/.*\.text$/,
-            handler: 'StaleWhileRevalidate',
-            options: {
-              cacheName: 'ponomar-bible',
-              expiration: { maxEntries: 100, maxAgeSeconds: 60 * 60 * 24 * 30 },
-            },
-          },
           {
             urlPattern: /\/fonts\/.*\.woff2?$/,
             handler: 'CacheFirst',