feat(sync): add full sync option for annotations in koplugin, closes #3710 (#3718)

Add "Full sync all annotations" menu item that pushes and pulls all
annotations regardless of the last sync timestamp, enabling users to
sync old highlights that were created before the plugin was installed.

Changes:
- Add full_sync parameter to push/pull that bypasses timestamp filter
  and uses since=0 for pulling all server annotations
- Deduplicate by annotation ID alongside position-based dedup
- Store server ID on pulled annotations and reuse it when pushing
- Parse ISO 8601 timestamps from server to preserve original
  created/updated dates instead of using current time
- Resolve KOReader page numbers from xpointers via getPageFromXPointer
- Resolve Readest page numbers from CFI via getCFIProgress on pull

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/readest.koplugin/main.lua

@@ -137,6 +137,15 @@ function ReadestSync:addToMainMenu(menu_items)
                 callback = function()
                     self:pullBookNotes(true)
                 end,
+            },
+            {
+                text = _("Full sync all annotations"),
+                enabled_func = function()
+                    return self.settings.access_token ~= nil and self.ui.document ~= nil
+                end,
+                callback = function()
+                    self:fullSyncBookNotes()
+                end,
                 separator = true,
             },
             {
@@ -227,22 +236,22 @@ end
 
 -- ── Annotation sync ────────────────────────────────────────────────
 
-function ReadestSync:pushBookNotes(interactive)
-    if interactive and NetworkMgr:willRerunWhenOnline(function() self:pushBookNotes(interactive) end) then
+function ReadestSync:pushBookNotes(interactive, full_sync)
+    if interactive and NetworkMgr:willRerunWhenOnline(function() self:pushBookNotes(interactive, full_sync) end) then
         return
     end
 
     local client = self:ensureClient(interactive)
     if not client then return end
 
-    SyncAnnotations:push(self.ui, self.settings, client, interactive)
+    SyncAnnotations:push(self.ui, self.settings, client, interactive, full_sync)
 end
 
-function ReadestSync:pullBookNotes(interactive)
+function ReadestSync:pullBookNotes(interactive, full_sync)
     local book_hash, meta_hash = self:getBookIdentifiers()
     if not book_hash or not meta_hash then return end
 
-    if NetworkMgr:willRerunWhenOnline(function() self:pullBookNotes(interactive) end) then
+    if NetworkMgr:willRerunWhenOnline(function() self:pullBookNotes(interactive, full_sync) end) then
         return
     end
 
@@ -250,10 +259,16 @@ function ReadestSync:pullBookNotes(interactive)
     if not client then return end
 
     SyncAnnotations:pull(
-        self.ui, self.settings, client, book_hash, meta_hash, self.dialog, interactive
+        self.ui, self.settings, client, book_hash, meta_hash, self.dialog, interactive, full_sync
     )
 end
 
+function ReadestSync:fullSyncBookNotes()
+    -- Push all annotations first, then pull all
+    self:pushBookNotes(true, true)
+    self:pullBookNotes(true, true)
+end
+
 -- ── Event handlers ─────────────────────────────────────────────────
 
 function ReadestSync:onReadestSyncToggleAutoSync(toggle)