Add authentication feature with session management

- Implemented authentication logic in src/server/auth.js, including session token creation and verification.
- Integrated authentication routes for login, logout, and user session retrieval in the Fastify server.
- Updated docker-compose.yml to include optional authentication environment variables.
- Added @fastify/cookie dependency for cookie management in package.json and package-lock.json.
- Enhanced the frontend with login form and session handling in App.svelte, including UI updates for authenticated states.
- Styled authentication components in app.css for better user experience.

package-lock.json

@@ -9,6 +9,7 @@
       "version": "1.0.0",
       "license": "ISC",
       "dependencies": {
+        "@fastify/cookie": "^11.1.2",
         "@fastify/static": "^10.1.2",
         "@picocss/pico": "^2.1.1",
         "adm-zip": "^0.5.17",
@@ -327,6 +328,39 @@
       "integrity": "sha512-NM8/P9n3XjXhIZn1lLhkFaACTOURQXjWhV4BA/RnOv8xvgqtqpAX9IO4mRQxSx1Rlo4tqzeqb0sOlruaOy3dug==",
       "license": "MIT"
     },
+    "node_modules/@fastify/cookie": {
+      "version": "11.1.2",
+      "resolved": "https://registry.npmjs.org/@fastify/cookie/-/cookie-11.1.2.tgz",
+      "integrity": "sha512-Dtrpk/YOGUsbRMvP/8ZqPpwnMRv0qSqodFdoQ2B589Obc7jw4s4Qla+cV72Bsm7WsZJnqlYFX/i7uSBq0xzg6g==",
+      "funding": [
+        {
+          "type": "github",
+          "url": "https://github.com/sponsors/fastify"
+        },
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/fastify"
+        }
+      ],
+      "license": "MIT",
+      "dependencies": {
+        "cookie": "^2.0.0",
+        "fastify-plugin": "^6.0.0"
+      }
+    },
+    "node_modules/@fastify/cookie/node_modules/cookie": {
+      "version": "2.0.1",
+      "resolved": "https://registry.npmjs.org/cookie/-/cookie-2.0.1.tgz",
+      "integrity": "sha512-yuToqVvRrj6pfDXREyQAAv8SkAEk/8GS3jQRTiUMm66TVtBYmqQeoEjL2Lmq8Rpo6271vH76InTChTitEAm65w==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=22"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/express"
+      }
+    },
     "node_modules/@fastify/error": {
       "version": "4.2.0",
       "resolved": "https://registry.npmjs.org/@fastify/error/-/error-4.2.0.tgz",