port: upstream PR #1342 - Book Info screen, richer metadata, safer controls

Ports upstream PR #1342 (feat: Add Book Info screen, richer metadata,
and safer file-browser controls) with mod-specific adaptations:

- Parse and cache series, seriesIndex, description from EPUB OPF
- Bump book.bin cache version to 6 for new metadata fields
- Add BookInfoActivity (new screen) accessible via Right button in FileBrowser
- Add ManageBook menu via Left button in FileBrowser (replaces upstream hidden delete)
- Guard all delete/archive actions with ConfirmationActivity (10 call sites)
- Add inputArmed gating to ConfirmationActivity to prevent accidental confirmation
- Safe deserialization: readString now returns bool with MAX_STRING_LENGTH guard
- Add series field to RecentBooksStore with JSON and binary serialization
- Add i18n keys: STR_BOOK_INFO, STR_AUTHOR, STR_SERIES, STR_FILE_SIZE, etc.

Made-with: Cursor

lib/Epub/Epub.h

@@ -51,6 +51,9 @@ class Epub {
   const std::string& getTitle() const;
   const std::string& getAuthor() const;
   const std::string& getLanguage() const;
+  const std::string& getSeries() const;
+  const std::string& getSeriesIndex() const;
+  const std::string& getDescription() const;
   std::string getCoverBmpPath(bool cropped = false) const;
   bool generateCoverBmp(bool cropped = false) const;
   std::string getThumbBmpPath() const;