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/api/src/error/handler.rs

@@ -0,0 +1,36 @@
+use axum::{
+    extract::rejection::JsonRejection,
+    http::StatusCode,
+    response::{IntoResponse, Response},
+    Json,
+};
+use sea_orm::DbErr;
+
+use app::error::UserError;
+
+use super::{ApiError, HTTPError};
+use crate::models::ApiErrorResponse;
+
+impl IntoResponse for ApiError {
+    fn into_response(self) -> Response {
+        let err = self.0;
+
+        let (status, message) = if let Some(err) = err.downcast_ref::<DbErr>() {
+            tracing::error!(%err, "error from db:");
+            (err.to_status_code(), "DB error".to_string()) // hide the detail
+        } else if let Some(err) = err.downcast_ref::<UserError>() {
+            (err.to_status_code(), err.to_string())
+        } else if let Some(err) = err.downcast_ref::<JsonRejection>() {
+            tracing::error!(%err, "error from extractor:");
+            (err.to_status_code(), err.to_string())
+        } else {
+            tracing::error!(%err, "error from other source:");
+            (
+                StatusCode::INTERNAL_SERVER_ERROR,
+                "Unknown error".to_string(),
+            )
+        };
+
+        (status, Json(ApiErrorResponse { message })).into_response()
+    }
+}