Fix configStore.loadConfig -> fetchConfig method name

The config store exports fetchConfig() but App.svelte was calling
the nonexistent loadConfig(), causing a TypeError that prevented
the sidecar from launching.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/App.svelte

@@ -61,7 +61,7 @@
       sidecarState = "starting";
       backendStore.setPort(8081);
       backendStore.connect();
-      configStore.loadConfig();
+      configStore.fetchConfig();
     }
   }
 
@@ -78,13 +78,13 @@
       log(`Sidecar ready on port ${port}`);
       backendStore.setPort(port);
       backendStore.connect();
-      configStore.loadConfig();
+      configStore.fetchConfig();
     } catch (err) {
       // If sidecar launch fails, still try connecting to default port
       log(`Sidecar launch failed: ${err}, trying default port`);
       sidecarState = "starting";
       backendStore.connect();
-      configStore.loadConfig();
+      configStore.fetchConfig();
     }
   }