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/RDEPUBBackgroundTrace.swift

@@ -0,0 +1,10 @@
+import Foundation
+
+enum RDEPUBBackgroundTrace {
+
+    static func log(_ scope: String, _ message: String) {
+        let threadRole = Thread.isMainThread ? "main" : "bg"
+        let queueLabel = String(validatingUTF8: __dispatch_queue_get_label(nil)) ?? "unknown"
+        print("[EPUB][\(scope)][\(threadRole)][queue=\(queueLabel)] \(message)")
+    }
+}