Task 10.3: Add "Forgot password?" link with toast and "Sign up" link to login page

- Install sonner for toast notifications
- Add handleForgotPassword function that shows "Not yet available" toast
- Add "Forgot password?" link next to password label
- Verify "Sign up" link to /register exists
- Add Toaster component to public layout
- Mark task 10.3 as [x] in tasks.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package-lock.json

@@ -27,6 +27,7 @@
         "pg": "^8.13.1",
         "react": "^19.2.4",
         "react-dom": "^19.2.4",
+        "sonner": "^2.0.7",
         "tailwind-merge": "^3.4.0",
         "zod": "^4.3.6"
       },
@@ -7282,6 +7283,16 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/sonner": {
+      "version": "2.0.7",
+      "resolved": "https://registry.npmjs.org/sonner/-/sonner-2.0.7.tgz",
+      "integrity": "sha512-W6ZN4p58k8aDKA4XPcx2hpIQXBRAgyiWVkYhT7CvK6D3iAu7xjvVyhQHg2/iaKJZ1XVJ4r7XuwGL+WGEK37i9w==",
+      "license": "MIT",
+      "peerDependencies": {
+        "react": "^18.0.0 || ^19.0.0 || ^19.0.0-rc",
+        "react-dom": "^18.0.0 || ^19.0.0 || ^19.0.0-rc"
+      }
+    },
     "node_modules/source-map": {
       "version": "0.6.1",
       "dev": true,