Make auth JWT-only for Capacitor WebView origins (#22)

Drop CSRF cookie dependency (js-cookie), store tokens via localStorage with
optional Capacitor Preferences mirror, and attach Authorization on every
request so Android/iOS shells work without third-party cookies.

llm-fe/package-lock.json

@@ -23,7 +23,6 @@
         "bootstrap": "^5.3.3",
         "chroma-js": "^3.1.2",
         "formik": "^2.4.6",
-        "js-cookie": "^3.0.5",
         "jwt-decode": "^4.0.0",
         "lodash": "^4.17.21",
         "markdown-to-jsx": "^7.7.2",
@@ -12814,14 +12813,6 @@
         "jiti": "bin/jiti.js"
       }
     },
-    "node_modules/js-cookie": {
-      "version": "3.0.5",
-      "resolved": "https://registry.npmjs.org/js-cookie/-/js-cookie-3.0.5.tgz",
-      "integrity": "sha512-cEiJEAEoIbWfCZYKWhVwFuvPX1gETRYPw6LlaTKoxD3s2AkXzkCjnp6h0V77ozyqj0jakteJ4YqDJT830+lVGw==",
-      "engines": {
-        "node": ">=14"
-      }
-    },
     "node_modules/js-tokens": {
       "version": "4.0.0",
       "resolved": "https://registry.npmjs.org/js-tokens/-/js-tokens-4.0.0.tgz",