refactor: rename RDReaderView -> RDEpubReaderView, update pod config and docs

- Rename source module from RDReaderView to RDEpubReaderView
- Move all source files from Sources/RDReaderView/ to Sources/RDEpubReaderView/
- Update podspec: RDReaderView.podspec -> RDEpubReaderView.podspec
- Update Podfile, demo project, and CocoaPods config for new pod name
- Delete old RDReaderView pod support files from ReadViewDemo/Pods
- Add new RDEpubReaderView pod support files
- Update documentation (API ref, architecture, UML, conventions, etc.)
- Add FixedLayoutRotationTests
- Update .gitignore: exclude .DS_Store, manual unpack backups, _ssoft-output

Sources/RDEpubReaderView/EPUBUI/ReaderController/ChapterRuntime/RDEPUBPageCountCache.swift

@@ -0,0 +1,33 @@
+import Foundation
+
+final class RDEPUBPageCountCache {
+
+    private var storage: [RDEPUBChapterCacheKey: RDEPUBRuntimePageCount] = [:]
+
+    private let lock = NSLock()
+
+    subscript(key: RDEPUBChapterCacheKey) -> RDEPUBRuntimePageCount? {
+        get {
+            lock.lock()
+            defer { lock.unlock() }
+            return storage[key]
+        }
+        set {
+            lock.lock()
+            defer { lock.unlock() }
+            storage[key] = newValue
+        }
+    }
+
+    func remove(forSpineIndex spineIndex: Int) {
+        lock.lock()
+        defer { lock.unlock() }
+        storage = storage.filter { $0.value.spineIndex != spineIndex }
+    }
+
+    func removeAll() {
+        lock.lock()
+        defer { lock.unlock() }
+        storage.removeAll()
+    }
+}