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/package.json

@@ -10,7 +10,9 @@
 		"preview": "vite preview",
 		"prepare": "svelte-kit sync || echo ''",
 		"check": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json",
-		"check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch"
+		"check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch",
+		"format": "prettier --write .",
+		"format:check": "prettier --check ."
 	},
 	"devDependencies": {
 		"@sveltejs/adapter-auto": "^7.0.0",
@@ -20,6 +22,8 @@
 		"@tailwindcss/vite": "^4.2.2",
 		"@types/node": "^25.5.2",
 		"openapi-typescript": "^7.13.0",
+		"prettier": "^3.8.4",
+		"prettier-plugin-svelte": "^4.1.0",
 		"svelte": "^5.54.0",
 		"svelte-check": "^4.4.2",
 		"tailwindcss": "^4.2.2",