HLE: Implement offline web applet with local HTTP server

Add a lightweight offline web rendering applet (LibAppletOff) that extracts HTML content from the game's Manual NCA, serves it via a local HTTP server, and injects NX JavaScript polyfills to capture applet callbacks.

Key changes:

• Add OfflineWebServer to serve extracted RomFS content and handle callback URLs (nx.endApplet, nx.sendMessage, localhost redirects)
• Rewrite BrowserApplet to extract and serve offline HTML content from Manual NCAs, with content-aware NCA selection for games that ship multiple Manual NCAs (e.g. AC3 Remastered)
• Add XCI/NSP fallback for Manual NCA discovery when ContentManager does not register them (common for XCI-loaded games)
• Store ApplicationPath on Switch for game file re-scanning
• Add DisplayWebPage to IHostUIHandler with Avalonia implementation
• Add WindowClosed to WebExitReason enum

Signed-off-by: Zephyron zephyron@citron-emu.org