mod: Phase 1 - bring forward mod-exclusive files with ActivityManager migration

Brings ~55 mod-exclusive files to the upstream-based mod/master-resync branch:

Activities (migrated to new ActivityManager pattern):
- Clock/Time: SetTimeActivity, SetTimezoneOffsetActivity, NtpSyncActivity
- Dictionary: DictionaryDefinitionActivity, DictionarySuggestionsActivity,
  DictionaryWordSelectActivity, LookedUpWordsActivity
- Bookmark: EpubReaderBookmarkSelectionActivity
- Book management: BookManageMenuActivity, EndOfBookMenuActivity
- OPDS: OpdsServerListActivity, OpdsSettingsActivity
- Utility: DirectoryPickerActivity, NumericStepperActivity

Utilities (unchanged):
- BookManager, BookSettings, BookmarkStore, BootNtpSync
- Dictionary, LookupHistory, TimeSync, OpdsServerStore

Libraries: PlaceholderCover, TableData, ChapterXPathIndexer
Scripts: inject_mod_version, generate_book_icon, preview_placeholder_cover
Docs: KOReader sync XPath mapping

Migration changes:
- ActivityWithSubactivity -> Activity base class
- Callback constructors -> finish()/setResult() pattern
- enterNewActivity() -> startActivityForResult()
- Activity::RenderLock&& -> RenderLock&&

These files won't compile yet - they reference mod settings and I18n
strings that will be added in subsequent phases.

Made-with: Cursor

chat-summaries/2026-02-17_summary.md

@@ -0,0 +1,17 @@
+# Cherry-pick upstream PR #939 — dangling pointer fix
+
+## Task
+Cherry-pick commit `b47e1f6` from upstream PR [#939](https://github.com/crosspoint-reader/crosspoint-reader/pull/939) into `mod/master`.
+
+## Changes
+- **File**: `src/activities/home/MyLibraryActivity.cpp` (lines 199-200)
+- **Fix**: Changed `folderName` from `auto` (deduced as `const char*` pointing to a temporary) to `std::string`, and called `.c_str()` at the point of use instead. This eliminates a dangling pointer caused by `.c_str()` on a temporary `std::string` from `basepath.substr(...)`.
+
+## Method
+- Fetched PR ref via `git fetch upstream pull/939/head:pr-939`
+- Cherry-picked `b47e1f6` — applied cleanly with no conflicts
+- Build verified: SUCCESS (PlatformIO, 68s)
+- Cleaned up temporary `pr-939` branch ref
+
+## Follow-up
+- None required. The commit preserves original authorship (Uri Tauber).