feat: rename ClawChat → PinchChat across entire project

- Update package.json name and repo URL
- Update README.md, CONTRIBUTING.md branding and links
- Update UI components (Header, Chat) display names
- Update gateway user-agent string
- Rename GitHub repo via API
- Mark FEEDBACK.md item #1 as done

src/lib/gateway.ts

@@ -77,7 +77,7 @@ export class GatewayClient {
       permissions: {},
       auth: { token: AUTH_TOKEN },
       locale: 'fr-FR',
-      userAgent: 'clawchat/1.0.0',
+      userAgent: 'pinchchat/1.0.0',
     }).then((res) => {
       console.log('[GW] connected!', res);
       this.connected = true;