perf(reader): split progress into its own store to cut React commit storm (#4557)

setProgress was called multiple times per swipe burst, each call writing
into readerStore.viewStates[key].progress. ~65 places in the reader
subtree subscribed to useReaderStore() without a selector, so every
setProgress fan-out re-rendered all of them -- even the 51 that didn't
care about progress. On Android release builds this showed up as
Layout = 9.8% and Function Call = 9.6% of main-thread self time in
Chrome DevTools' Bottom-Up profile during a reading session.

Fix:
- New tiny store store/readerProgressStore.ts holds the per-book
  BookProgress map. setBookProgress only fires its own subscribers.
- readerStore.setProgress now writes progress to the new store and only
  touches bookDataStore for the primary view (secondary parallel views
  shouldn't overwrite the shared config).
- readerStore.getProgress is kept as a delegating facade so existing
  imperative call sites don't break.
- Components / hooks that genuinely need to react to progress changes
  subscribe via the new useBookProgress(bookKey) hook. The handful of
  call sites that just want a one-shot read use getBookProgress(key) so
  they don't subscribe at all.
- readerStore.clearViewState calls clearBookProgress so the map doesn't
  grow unbounded across book opens/closes.

See store/readerProgressStore.ts header for the full rationale.

apps/readest-app/src/app/reader/hooks/useTTSControl.ts

@@ -4,6 +4,7 @@ import { useAuth } from '@/context/AuthContext';
 import { useThemeStore } from '@/store/themeStore';
 import { useBookDataStore } from '@/store/bookDataStore';
 import { useReaderStore } from '@/store/readerStore';
+import { useBookProgress } from '@/store/readerProgressStore';
 import { useProofreadStore } from '@/store/proofreadStore';
 import { TransformContext } from '@/services/transformers/types';
 import { proofreadTransformer } from '@/services/transformers/proofread';
@@ -30,9 +31,12 @@ export const useTTSControl = ({ bookKey, onRequestHidePanel }: UseTTSControlProp
   const { appService } = useEnv();
   const { user } = useAuth();
   const { isDarkMode } = useThemeStore();
-  const { getBookData } = useBookDataStore();
-  const { getView, getProgress, getViewSettings } = useReaderStore();
-  const { setViewSettings, setTTSEnabled } = useReaderStore();
+  const getBookData = useBookDataStore((s) => s.getBookData);
+  const getView = useReaderStore((s) => s.getView);
+  const getProgress = useReaderStore((s) => s.getProgress);
+  const getViewSettings = useReaderStore((s) => s.getViewSettings);
+  const setViewSettings = useReaderStore((s) => s.setViewSettings);
+  const setTTSEnabled = useReaderStore((s) => s.setTTSEnabled);
   const { getMergedRules } = useProofreadStore();
 
   const [ttsLang, setTtsLang] = useState<string>('en');
@@ -265,8 +269,10 @@ export const useTTSControl = ({ bookKey, onRequestHidePanel }: UseTTSControlProp
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [ttsController, bookKey]);
 
-  // Location tracking — re-highlight when progress changes
-  const progress = getProgress(bookKey);
+  // Location tracking — re-highlight when progress changes.
+  // Reactive subscription via readerProgressStore so the effect below
+  // re-runs on page turns without dragging in the whole readerStore.
+  const progress = useBookProgress(bookKey);
   useEffect(() => {
     const ttsController = ttsControllerRef.current;
     if (!ttsController) return;