feat: Adds SPA fallback route to server

Implements a SPA fallback route that serves index.html for unmatched routes.

This enables client-side routing for dynamic routes when using embedded static files.
Excludes API routes from the fallback to ensure they are handled by dedicated handlers.
Also includes the required headers by pyodide (python interpreter)

Sets ssr to false in the layout.ts file to disable server-side rendering for the entire application.
This enables client-side rendering for the entire application.

Also refactors code copy function in Markdown component.

Author: allozaur

tools/server/server.cpp

@@ -4911,6 +4911,42 @@ int main(int argc, char ** argv) {
     svr->Get (params.api_prefix + "/slots",               handle_slots);
     svr->Post(params.api_prefix + "/slots/:id_slot",      handle_slots_action);
 
+    // SPA fallback route - serve index.html for any route that doesn't match API endpoints
+    // This enables client-side routing for dynamic routes like /chat/[id]
+    if (params.public_path.empty()) {
+        // Only add fallback when using embedded static files
+        svr->Get(".*", [](const httplib::Request & req, httplib::Response & res) {
+            // Skip API routes - they should have been handled above
+            if (req.path.find("/v1/") != std::string::npos || 
+                req.path.find("/health") != std::string::npos ||
+                req.path.find("/metrics") != std::string::npos ||
+                req.path.find("/props") != std::string::npos ||
+                req.path.find("/models") != std::string::npos ||
+                req.path.find("/api/tags") != std::string::npos ||
+                req.path.find("/completions") != std::string::npos ||
+                req.path.find("/chat/completions") != std::string::npos ||
+                req.path.find("/embeddings") != std::string::npos ||
+                req.path.find("/tokenize") != std::string::npos ||
+                req.path.find("/detokenize") != std::string::npos ||
+                req.path.find("/lora-adapters") != std::string::npos ||
+                req.path.find("/slots") != std::string::npos) {
+                return false; // Let other handlers process API routes
+            }
+            
+            // Serve index.html for all other routes (SPA fallback)
+            if (req.get_header_value("Accept-Encoding").find("gzip") == std::string::npos) {
+                res.set_content("Error: gzip is not supported by this browser", "text/plain");
+            } else {
+                res.set_header("Content-Encoding", "gzip");
+                // COEP and COOP headers, required by pyodide (python interpreter)
+                res.set_header("Cross-Origin-Embedder-Policy", "require-corp");
+                res.set_header("Cross-Origin-Opener-Policy", "same-origin");
+                res.set_content(reinterpret_cast<const char*>(index_html_gz), index_html_gz_len, "text/html; charset=utf-8");
+            }
+            return false;
+        });
+    }
+
     //
     // Start the server
     //

tools/server/webui/src/lib/components/app/MarkdownContent.svelte

@@ -7,6 +7,7 @@
 	import remarkRehype from 'remark-rehype';
 	import rehypeKatex from 'rehype-katex';
 	import rehypeStringify from 'rehype-stringify';
+	import { copyCodeToClipboard } from '$lib/utils/copy';
 	import 'highlight.js/styles/github-dark.css';
 	import 'katex/dist/katex.min.css';
 
@@ -143,7 +144,6 @@
 				}
 
 				try {
-					const { copyCodeToClipboard } = await import('$lib/utils/copy');
 					await copyCodeToClipboard(rawCode);
 				} catch (error) {
 					console.error('Failed to copy code:', error);

tools/server/webui/src/routes/+layout.ts

@@ -0,0 +1,3 @@
+export const ssr = false;
+export const csr = true;
+export const prerender = false;