feat: separate AGPL libraries and add dynamic WASM loading

- Add WASM settings page for configuring external AGPL modules
- Implement dynamic loading for PyMuPDF, Ghostscript, and CoherentPDF
- Add Cloudflare Worker proxy for serving WASM files with CORS
- Update all affected tool pages to check WASM availability
- Add showWasmRequiredDialog for missing module configuration

Documentation:
- Update README, licensing.html, and docs to clarify AGPL components
  are not bundled and must be configured separately
- Add WASM-PROXY.md deployment guide with recommended source URLs
- Rename "CPDF" to "CoherentPDF" for consistency

public/workers/table-of-contents.worker.d.ts

@@ -7,6 +7,7 @@ interface GenerateTOCMessage {
   fontSize: number;
   fontFamily: number;
   addBookmark: boolean;
+  cpdfUrl?: string;
 }
 
 interface TOCSuccessResponse {