refactor: migrate contact form to TanStack Form

- Replace manual state management with @tanstack/react-form
- Add proper Field/FieldLabel components for accessibility
- Simplify server action (remove useActionState signature)
- Remove use-debounce dependency
- Update PGP key links and minor styling tweaks

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pnpm-lock.yaml

@@ -89,6 +89,9 @@ importers:
       '@t3-oss/env-nextjs':
         specifier: ^0.13.10
         version: 0.13.10(typescript@5.9.3)(zod@4.3.6)
+      '@tanstack/react-form':
+        specifier: ^1.28.0
+        version: 1.28.0(react-dom@19.2.4(react@19.2.4))(react@19.2.4)
       '@vercel/analytics':
         specifier: ^1.6.1
         version: 1.6.1(next@16.1.6(@babel/core@7.28.6)(babel-plugin-react-compiler@19.1.0-rc.3)(react-dom@19.2.4(react@19.2.4))(react@19.2.4))(react@19.2.4)
@@ -242,9 +245,6 @@ importers:
       unified:
         specifier: ^11.0.5
         version: 11.0.5
-      use-debounce:
-        specifier: ^10.1.0
-        version: 10.1.0(react@19.2.4)
       zod:
         specifier: ^4.3.6
         version: 4.3.6
@@ -1970,6 +1970,38 @@ packages:
     peerDependencies:
       tailwindcss: '>=3.0.0 || insiders || >=4.0.0-alpha.20 || >=4.0.0-beta.1'
 
+  '@tanstack/devtools-event-client@0.4.0':
+    resolution: {integrity: sha512-RPfGuk2bDZgcu9bAJodvO2lnZeHuz4/71HjZ0bGb/SPg8+lyTA+RLSKQvo7fSmPSi8/vcH3aKQ8EM9ywf1olaw==}
+    engines: {node: '>=18'}
+
+  '@tanstack/form-core@1.28.0':
+    resolution: {integrity: sha512-MX3YveB6SKHAJ2yUwp+Ca/PCguub8bVEnLcLUbFLwdkSRMkP0lMGdaZl+F0JuEgZw56c6iFoRyfILhS7OQpydA==}
+
+  '@tanstack/pacer-lite@0.1.1':
+    resolution: {integrity: sha512-y/xtNPNt/YeyoVxE/JCx+T7yjEzpezmbb+toK8DDD1P4m7Kzs5YR956+7OKexG3f8aXgC3rLZl7b1V+yNUSy5w==}
+    engines: {node: '>=18'}
+
+  '@tanstack/react-form@1.28.0':
+    resolution: {integrity: sha512-ibLcf5QkTogV0Ly944CuqGxWTpHyreNA4Cy8Wtky7zE9wtE3HVapQt4/hUuXo51zihfTkv5URiXpoTSKF5Xosg==}
+    peerDependencies:
+      '@tanstack/react-start': '*'
+      react: ^17.0.0 || ^18.0.0 || ^19.0.0
+    peerDependenciesMeta:
+      '@tanstack/react-start':
+        optional: true
+
+  '@tanstack/react-store@0.8.0':
+    resolution: {integrity: sha512-1vG9beLIuB7q69skxK9r5xiLN3ztzIPfSQSs0GfeqWGO2tGIyInZx0x1COhpx97RKaONSoAb8C3dxacWksm1ow==}
+    peerDependencies:
+      react: ^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0
+      react-dom: ^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0
+
+  '@tanstack/store@0.7.7':
+    resolution: {integrity: sha512-xa6pTan1bcaqYDS9BDpSiS63qa6EoDkPN9RsRaxHuDdVDNntzq3xNwR5YKTU/V3SkSyC9T4YVOPh2zRQN0nhIQ==}
+
+  '@tanstack/store@0.8.0':
+    resolution: {integrity: sha512-Om+BO0YfMZe//X2z0uLF2j+75nQga6TpTJgLJQBiq85aOyZNIhkCgleNcud2KQg4k4v9Y9l+Uhru3qWMPGTOzQ==}
+
   '@tybys/wasm-util@0.10.1':
     resolution: {integrity: sha512-9tTaPJLSiejZKx+Bmog4uSubteqTvFrVrURwkmHixBo0G4seD0zUxp98E1DzUBJxLQ3NPwXrGKDiVjwx/DpPsg==}
 
@@ -5052,12 +5084,6 @@ packages:
       '@types/react':
         optional: true
 
-  use-debounce@10.1.0:
-    resolution: {integrity: sha512-lu87Za35V3n/MyMoEpD5zJv0k7hCn0p+V/fK2kWD+3k2u3kOCwO593UArbczg1fhfs2rqPEnHpULJ3KmGdDzvg==}
-    engines: {node: '>= 16.0.0'}
-    peerDependencies:
-      react: '*'
-
   use-sidecar@1.1.3:
     resolution: {integrity: sha512-Fedw0aZvkhynoPYlA5WXrMCAMm+nSWdZt6lzJQ7Ok8S6Q+VsHmHpRWndVRJ8Be0ZbkfPc5LRYH+5XrzXcEeLRQ==}
     engines: {node: '>=10'}
@@ -6695,6 +6721,35 @@ snapshots:
       postcss-selector-parser: 6.0.10
       tailwindcss: 4.1.18
 
+  '@tanstack/devtools-event-client@0.4.0': {}
+
+  '@tanstack/form-core@1.28.0':
+    dependencies:
+      '@tanstack/devtools-event-client': 0.4.0
+      '@tanstack/pacer-lite': 0.1.1
+      '@tanstack/store': 0.7.7
+
+  '@tanstack/pacer-lite@0.1.1': {}
+
+  '@tanstack/react-form@1.28.0(react-dom@19.2.4(react@19.2.4))(react@19.2.4)':
+    dependencies:
+      '@tanstack/form-core': 1.28.0
+      '@tanstack/react-store': 0.8.0(react-dom@19.2.4(react@19.2.4))(react@19.2.4)
+      react: 19.2.4
+    transitivePeerDependencies:
+      - react-dom
+
+  '@tanstack/react-store@0.8.0(react-dom@19.2.4(react@19.2.4))(react@19.2.4)':
+    dependencies:
+      '@tanstack/store': 0.8.0
+      react: 19.2.4
+      react-dom: 19.2.4(react@19.2.4)
+      use-sync-external-store: 1.6.0(react@19.2.4)
+
+  '@tanstack/store@0.7.7': {}
+
+  '@tanstack/store@0.8.0': {}
+
   '@tybys/wasm-util@0.10.1':
     dependencies:
       tslib: 2.8.1
@@ -10378,10 +10433,6 @@ snapshots:
     optionalDependencies:
       '@types/react': 19.2.10
 
-  use-debounce@10.1.0(react@19.2.4):
-    dependencies:
-      react: 19.2.4
-
   use-sidecar@1.1.3(@types/react@19.2.10)(react@19.2.4):
     dependencies:
       detect-node-es: 1.1.0