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

src/JsonSettingsIO.cpp

@@ -283,6 +283,7 @@ bool JsonSettingsIO::saveRecentBooks(const RecentBooksStore& store, const char*
     obj["path"] = book.path;
     obj["title"] = book.title;
     obj["author"] = book.author;
+    obj["series"] = book.series;
     obj["coverBmpPath"] = book.coverBmpPath;
   }
 
@@ -307,6 +308,7 @@ bool JsonSettingsIO::loadRecentBooks(RecentBooksStore& store, const char* json)
     book.path = obj["path"] | std::string("");
     book.title = obj["title"] | std::string("");
     book.author = obj["author"] | std::string("");
+    book.series = obj["series"] | std::string("");
     book.coverBmpPath = obj["coverBmpPath"] | std::string("");
     store.recentBooks.push_back(book);
   }