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-lock.json

@@ -15,6 +15,8 @@
 				"@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",
@@ -2210,6 +2212,36 @@
 				"node": "^10 || ^12 || >=14"
 			}
 		},
+		"node_modules/prettier": {
+			"version": "3.8.4",
+			"resolved": "https://registry.npmjs.org/prettier/-/prettier-3.8.4.tgz",
+			"integrity": "sha512-N2MylSdi48+5N/6S5j+maeHbUSIzzZ5uOcX5Hm4QpV8Dkb1HFjfAKTKX6yNPJQD9AhcT3ifHNB66tWTTJDi11Q==",
+			"dev": true,
+			"license": "MIT",
+			"bin": {
+				"prettier": "bin/prettier.cjs"
+			},
+			"engines": {
+				"node": ">=14"
+			},
+			"funding": {
+				"url": "https://github.com/prettier/prettier?sponsor=1"
+			}
+		},
+		"node_modules/prettier-plugin-svelte": {
+			"version": "4.1.0",
+			"resolved": "https://registry.npmjs.org/prettier-plugin-svelte/-/prettier-plugin-svelte-4.1.0.tgz",
+			"integrity": "sha512-YZkhA2Q9oOerFFG9tq+2f98WYT7Z2JgrybJrAyrB78jpsH9i/DdgplXemehuFPgsldetFNCcR/yCcYlDjPy94Q==",
+			"dev": true,
+			"license": "MIT",
+			"engines": {
+				"node": ">=20"
+			},
+			"peerDependencies": {
+				"prettier": "^3.0.0",
+				"svelte": "^5.0.0"
+			}
+		},
 		"node_modules/readdirp": {
 			"version": "4.1.2",
 			"resolved": "https://registry.npmjs.org/readdirp/-/readdirp-4.1.2.tgz",