style(project): format Go with gofmt, set up Prettier for the frontend

Run gofmt -w across the backend, normalising the manually-aligned := blocks
to the gofmt standard. No code behaviour changes.

Add Prettier (+ prettier-plugin-svelte) to the frontend with the SvelteKit
default config (tabs, single quotes) so formatting is reproducible, then run
it over the whole tree. Add format / format:check npm scripts and a
.prettierignore (build output, generated schema.ts, static assets).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/api/auth.ts

@@ -8,7 +8,7 @@ export async function login(name: string, password: string): Promise<void> {
 	authStore.update((s) => ({
 		...s,
 		accessToken: tokens.access_token ?? null,
-		refreshToken: tokens.refresh_token ?? null,
+		refreshToken: tokens.refresh_token ?? null
 	}));
 }
 
@@ -28,7 +28,7 @@ export async function refresh(): Promise<void> {
 	authStore.update((s) => ({
 		...s,
 		accessToken: tokens.access_token ?? null,
-		refreshToken: tokens.refresh_token ?? null,
+		refreshToken: tokens.refresh_token ?? null
 	}));
 }
 
@@ -42,4 +42,4 @@ export function listSessions(params?: { offset?: number; limit?: number }): Prom
 
 export function terminateSession(sessionId: number): Promise<void> {
 	return api.delete<void>(`/auth/sessions/${sessionId}`);
-}
+}