feat: Integrate PR #857 dictionary intelligence and sub-activity refactor

Pull in the full feature update from PR #857 while preserving fork
advantages (HTML parsing, custom drawHints, PageForward/PageBack,
cache management, stardictCmp, /.dictionary/ paths).

- Add morphological stemming (getStemVariants), Levenshtein edit
  distance, and fuzzy matching (findSimilar) to Dictionary
- Create DictionarySuggestionsActivity for "Did you mean?" flow
- Add onDone callback to DictionaryDefinitionActivity for direct
  exit-to-reader via "Done" button
- Refactor DictionaryWordSelectActivity to ActivityWithSubactivity
  with cascading lookup (exact → stems → suggestions → not found),
  en-dash/em-dash splitting, and cross-page hyphenation
- Refactor LookedUpWordsActivity with reverse-chronological order,
  inline cascading lookup, UITheme-aware rendering, and sub-activities
- Simplify EpubReaderActivity LOOKUP/LOOKED_UP_WORDS handlers

Co-authored-by: Cursor <cursoragent@cursor.com>

src/activities/reader/EpubReaderActivity.h

@@ -5,7 +5,6 @@
 #include <freertos/semphr.h>
 #include <freertos/task.h>
 
-#include "DictionaryDefinitionActivity.h"
 #include "DictionaryWordSelectActivity.h"
 #include "EpubReaderMenuActivity.h"
 #include "LookedUpWordsActivity.h"