feat(docs): add documentation site and demo features

- Introduced a new documentation site for Cursor BYOK using Next.js and Fumadocs.
- Added a product demo page with a corresponding Vite configuration.
- Implemented a demo API to simulate LLM calls and responses.
- Enhanced the Makefile to include new build and development commands for the documentation.
- Updated package.json scripts for building and running the documentation site.
- Created various components and layouts for the documentation structure, including blog and user documentation sections.
- Added styling for the new components and layouts to ensure a cohesive design.
- Included a README and other necessary files for local development and deployment.

Makefile

@@ -1,16 +1,20 @@
 LOCAL_TAURI_SIGNING_KEY := $(CURDIR)/.tauri/cursor-byok.local.key
 
-.PHONY: check dev-web dev-server dev-desktop build-web build-server build-desktop build-docker
+.PHONY: check dev-web dev-docs dev-server dev-desktop build-web build-docs build-server build-desktop build-docker
 
 check:
 	cargo fmt --all -- --check
 	cargo clippy --workspace --all-targets -- -D warnings
 	cargo test --workspace --all-targets
 	npm --prefix apps/desktop run check
+	npm --prefix apps/docs run check
 
 dev-web:
 	npm --prefix apps/desktop run dev:web
 
+dev-docs:
+	npm --prefix apps/docs run dev
+
 dev-server:
 	CURSOR_CONSOLE_DIR=apps/desktop/dist cargo run --package cursor-server --bin cursor-server
 
@@ -20,6 +24,9 @@ dev-desktop:
 build-web:
 	npm --prefix apps/desktop run build
 
+build-docs:
+	npm --prefix apps/docs run build
+
 build-server:
 	cargo build --release --package cursor-server --bin cursor-server