fix(build): add terser as explicit devDependency

vite.config.js uses `minify: 'terser'` with custom terserOptions for
drop_console / drop_debugger in production builds, but terser is only
an optional peer dep of Vite since v3. It was sitting in package-lock.json
as a transitive, which `npm ci` installed strictly but `npm install`
(now used on PR CI to tolerate Dependabot lockfile drift) would
dedupe away. Declaring it explicitly ensures it's always installed.

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

Author: beihaili

package-lock.json

@@ -77,6 +77,7 @@
     "prettier": "^3.2.4",
     "satori": "^0.26.0",
     "tailwindcss": "^3.4.18",
+    "terser": "^5.46.1",
     "vite": "^4.5.14",
     "vitest": "^4.0.18"
   },