feat(rotate,delete-pages): Add custom rotation angles and enhance page management UI

- Add TypeScript type definitions for merge and alternate-merge Web Workers
- Implement custom rotation angle input with increment/decrement controls for rotate tool
- Extend delete-pages tool to render page thumbnails for better UX
- Hide number input spin buttons across all number inputs via CSS
- Refactor rotateAll function to accept angle parameter instead of direction multiplier
- Update fileHandler to support delete-pages tool thumbnail rendering
- Improve type safety in alternate-merge logic with proper interface definitions
- Enhance rotate tool UI with custom angle input field and adjustment buttons

public/workers/merge.worker.d.ts

@@ -0,0 +1,33 @@
+declare const coherentpdf: typeof import('../../src/types/coherentpdf.global').coherentpdf;
+
+interface MergeJob {
+    fileName: string;
+    rangeType: 'all' | 'specific' | 'single' | 'range';
+    rangeString?: string;
+    pageIndex?: number;
+    startPage?: number;
+    endPage?: number;
+}
+
+interface MergeFile {
+    name: string;
+    data: ArrayBuffer;
+}
+
+interface MergeMessage {
+    command: 'merge';
+    files: MergeFile[];
+    jobs: MergeJob[];
+}
+
+interface MergeSuccessResponse {
+    status: 'success';
+    pdfBytes: ArrayBuffer;
+}
+
+interface MergeErrorResponse {
+    status: 'error';
+    message: string;
+}
+
+type MergeResponse = MergeSuccessResponse | MergeErrorResponse;