feat: initialize thoughts-frontend with Next.js, TypeScript, and ESLint

- Add ESLint configuration for Next.js and TypeScript support.
- Create Next.js configuration file with standalone output option.
- Initialize package.json with scripts for development, build, and linting.
- Set up PostCSS configuration for Tailwind CSS.
- Add SVG assets for UI components.
- Create TypeScript configuration for strict type checking and module resolution.

thoughts-backend/app/src/state.rs

@@ -0,0 +1,6 @@
+use sea_orm::DatabaseConnection;
+
+#[derive(Clone)]
+pub struct AppState {
+    pub conn: DatabaseConnection,
+}