fix: Switch to xpath map for paragraph level syncing in KOSync (#1686)

Switch KOReader sync progress mapping from chapter matching to
XPath-based mapping.

- resolves KOReader positions using real XHTML ancestry paths
- supports paragraph-based upload mapping with text offsets
where needed
- passes the current paragraph index into sync so uploads map
back to KOReader more accurately

No HTTP client changes are included. No reader-state or resume-flow
changes are included.

---------

Co-authored-by: jpirnay <jens@pirnay.com>

src/activities/reader/KOReaderSyncActivity.h

@@ -3,6 +3,7 @@
 
 #include <functional>
 #include <memory>
+#include <optional>
 
 #include "KOReaderSyncClient.h"
 #include "ProgressMapper.h"
@@ -22,13 +23,15 @@ class KOReaderSyncActivity final : public Activity {
  public:
   explicit KOReaderSyncActivity(GfxRenderer& renderer, MappedInputManager& mappedInput,
                                 const std::shared_ptr<Epub>& epub, const std::string& epubPath, int currentSpineIndex,
-                                int currentPage, int totalPagesInSpine)
+                                int currentPage, int totalPagesInSpine,
+                                std::optional<uint16_t> currentParagraphIndex = std::nullopt)
       : Activity("KOReaderSync", renderer, mappedInput),
         epub(epub),
         epubPath(epubPath),
         currentSpineIndex(currentSpineIndex),
         currentPage(currentPage),
         totalPagesInSpine(totalPagesInSpine),
+        currentParagraphIndex(currentParagraphIndex),
         remoteProgress{},
         remotePosition{},
         localProgress{} {}
@@ -58,6 +61,7 @@ class KOReaderSyncActivity final : public Activity {
   int currentSpineIndex;
   int currentPage;
   int totalPagesInSpine;
+  std::optional<uint16_t> currentParagraphIndex;
 
   State state = WIFI_SELECTION;
   std::string statusMessage;