Position persistence during orientation change (#64)

* Fixed PDF reading position restoration during orientation change

* Refactored navigation logic in `EpubReaderScreen` and `PaginatedReader` to improve position restoration and UI consistency.

- Renamed `isNavigatingToBookmark` to `isNavigatingToPosition` and updated the overlay UI to reflect general position navigation.
- Added an orientation change listener to restore the reading position in `VERTICAL_SCROLL` mode using the last known locator.
- Improved highlight navigation in `VERTICAL_SCROLL` and `PAGINATED` modes, including chunk injection logic for highlights and fallback pagination logic.
- Implemented an anchor locator mechanism in `PaginatedReader` to preserve the reading position during layout constraint changes (e.g., orientation or resizing).

app/src/main/java/com/aryan/reader/paginatedreader/PaginatedReader.kt

@@ -530,6 +530,20 @@ fun PaginatedReaderScreen(
         var debouncedTextAlign by remember { mutableStateOf(textAlign) }
 
         var anchorLocatorForReconfig by remember { mutableStateOf<Locator?>(null) }
+        val currentPaginatorRef = remember { mutableStateOf<IPaginator?>(null) }
+
+        val previousConstraints = remember { arrayOf(this.constraints) }
+        if (previousConstraints[0] != this.constraints) {
+            val activePaginator = currentPaginatorRef.value
+            if (activePaginator is BookPaginator) {
+                val currentPage = pagerState.currentPage
+                val locator = activePaginator.getLocatorForPage(currentPage)
+                if (locator != null) {
+                    anchorLocatorForReconfig = locator
+                }
+            }
+            previousConstraints[0] = this.constraints
+        }
 
         val textStyle = remember(
             baseTextStyle,
@@ -556,8 +570,6 @@ fun PaginatedReaderScreen(
             )
         }
 
-        val currentPaginatorRef = remember { mutableStateOf<IPaginator?>(null) }
-
         LaunchedEffect(fontSizeMultiplier, lineHeightMultiplier, fontFamily, textAlign) {
             if (fontSizeMultiplier != debouncedFontSizeMult || lineHeightMultiplier != debouncedLineHeightMult || fontFamily != debouncedFontFamily || textAlign != debouncedTextAlign) {
                 Timber.d("Formatting changed. Waiting for debounce.")
@@ -2902,7 +2914,7 @@ private fun PaginatedTextSelectionMenu(
     onHighlight: ((HighlightColor) -> Unit)?,
     onDelete: (() -> Unit)?,
     @Suppress("unused") isProUser: Boolean,
-    isOss: Boolean,
+    @Suppress("unused") isOss: Boolean,
     activeHighlightPalette: List<HighlightColor> = emptyList(),
     onOpenPaletteManager: (() -> Unit)? = null
 ) {