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/README.md

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+# clean-axum
+
+Axum scaffold with clean architecture.
+
+You probably don't need [Rust on Rails](https://github.com/loco-rs/loco).
+
+Refer to [this post](https://kigawas.me/posts/rustacean-clean-architecture-approach/) for rationale and background.
+
+## Features
+
+- [Axum](https://github.com/tokio-rs/axum) framework
+- [SeaORM](https://github.com/SeaQL/sea-orm) domain models
+- Completely separated API routers and DB-related logic (named "persistence" layer)
+- Completely separated input parameters, queries and output schemas
+- OpenAPI documentation ([Swagger UI](https://clean-axum.shuttleapp.rs/docs) and [Scalar](https://clean-axum.shuttleapp.rs/scalar)) powered by [Utoipa](https://github.com/juhaku/utoipa)
+- Error handling with [Anyhow](https://github.com/dtolnay/anyhow)
+- Custom parameter validation with [validator](https://github.com/Keats/validator)
+- Optional [Shuttle](https://www.shuttle.rs/) runtime
+- Optional [prefork](https://docs.rs/prefork/latest/prefork/) workers for maximizing performance on Linux
+
+## Module hierarchy
+
+### API logic
+
+- `api::routers`: Axum endpoints
+- `api::error`: Models and traits for error handling
+- `api::extractor` Custom Axum extractors
+  - `api::extractor::json`: `Json` for bodies and responses
+  - `api::extractor::valid`: `Valid` for JSON body validation
+- `api::validation`: JSON validation model based on `validator`
+- `api::models`: Non domain model API models
+  - `api::models::response`: JSON error response
+
+### OpenAPI documentation
+
+- `doc`: Utoipa doc declaration
+
+### API-agonistic application logic
+
+Main concept: Web framework is replaceable.
+
+All modules here should not include any specific API web framework logic.
+
+- `app::persistence`: DB manipulation (CRUD) functions
+- `app::config`: DB or API server configuration
+- `app::state`: APP state, e.g. DB connection
+- `app::error`: APP errors used by `api::error`. e.g. "User not found"
+
+### DB/API-agnostic domain models
+
+Main concept: Database (Sqlite/MySQL/PostgreSQL) is replaceable.
+
+Except `models::domains` and `migration`, all modules are ORM library agnostic.
+
+- `models::domains`: SeaORM domain models
+- `models::params`: Serde input parameters for creating/updating domain models in DB
+- `models::schemas`: Serde output schemas for combining different domain models
+- `models::queries`: Serde queries for filtering domain models
+- `migration`: SeaORM migration files
+
+### Unit and integration tests
+
+- `tests::api`: API integration tests. Hierarchy is the same as `api::routers`
+- `tests::app::persistence`: DB/ORM-related unit tests. Hierarchy is the same as `app::persistence`
+
+### Others
+
+- `utils`: Utility functions
+- `main`: Tokio and Shuttle conditional entry point
+
+## Run
+
+### Start server
+
+```bash
+cp .env.example .env
+# touch dev.db
+# cargo install sea-orm-cli
+# sea-orm-cli migrate up
+cargo run
+
+# or for production
+cargo run --release
+```
+
+### Call API
+
+```bash
+curl -X POST http://localhost:3000/users -H "Content-Type: application/json" -d '{"username":"aaa"}'
+curl -X POST http://localhost:3000/users -H "Content-Type: application/json" -d '{"username":"abc"}'
+curl http://localhost:3000/users\?username\=a
+```
+
+### OpenAPI doc (Swagger UI/Scalar)
+
+```bash
+open http://localhost:3000/docs
+open http://localhost:3000/scalar
+```
+
+## Start Shuttle local server
+
+```bash
+# cargo install cargo-shuttle
+cargo shuttle run
+```
+
+Make sure docker engine is running, otherwise:
+
+```bash
+brew install colima docker
+colima start
+sudo ln -sf $HOME/.colima/default/docker.sock /var/run/docker.sock
+```
+
+## Shuttle deployment
+
+```bash
+cargo shuttle login
+cargo shuttle deploy
+```
+
+## Benchmark
+
+```bash
+# edit .env to use Postgres
+cargo run --release
+wrk --latency -t20 -c50 -d10s http://localhost:3000/users\?username\=
+```