Update doc

CLAUDE.md

@@ -1,39 +1,54 @@
 # CLAUDE.md
 
-This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
-
-## Overview
-
-Bitcoin price tracker UI — Python FastAPI web application. Serves an HTML/Tailwind page with live price updates streamed from btcdata (separate service) via WebSocket using HTMX.
+Bitcoin price tracker UI — Python FastAPI web application. Serves the HTML/Tailwind UI and
+proxies live price data from btcdata over WebSocket.
 
 ## Build & Development Commands
 
-- `make run` — Start dev server on port 4000 (connects to btcdata at BTCDATA_URL from `.env`)
-- `make run-local` — Start dev server using BTCDATA_LOCAL_URL from `.env`
-- `make tailwind` — Watch Tailwind CSS for changes (run in separate terminal)
-- `make test` — Run tests with pytest (`tests/` directory)
-- `npm run css:build` — One-off Tailwind CSS build
+- `make run` — Start dev server on port 4000; creates `.venv` and installs `requirements.txt`
+  on first run (the `venv` target, keyed off `requirements.txt`)
+- `cp .env.example .env` — optional; `.env` is `-include`d, so a missing one is not fatal
+- `make run-local` — Same, but with `BTCDATA_URL=$BTCDATA_LOCAL_URL`
+- `make tailwind` — Watch Tailwind CSS for changes
+- `make test` — Runs `pytest tests/`, but there is no `tests/` directory yet and pytest is not
+  in `requirements.txt`
+- `make venv` — Bootstrap the virtualenv without starting the server
 
 ## Docker
 
 Docker runs alongside local dev on different ports:
 
-| Service  | Local dev      | Docker         |
-|----------|----------------|----------------|
-| btcprice | localhost:4000 | localhost:4041 |
-| btcdata  | localhost:4100 | localhost:4101 |
+| Service  | Local dev      | Docker                               |
+|----------|----------------|--------------------------------------|
+| btcprice | localhost:4000 | localhost:4041 (container port 4040) |
+| btcdata  | localhost:4100 | localhost:4102                       |
 
-Uses external `btc-network` Docker network. btcdata must be running separately (or via its own docker-compose).
+`docker compose up -d` here starts **btcprice only**. Both projects attach to the external
+`btc-network` (`docker network create btc-network` once), and btcdata must be started from
+`../btcdata`. Inside the network btcprice reaches it at `http://btcdata:${DOCKER_BTCDATA_PORT:-4102}`.
+
+Note: `Dockerfile` bakes in a stale `ENV BTCDATA_URL=http://btcdata:4101`; compose always
+overrides it, so it only matters if the image is run outside compose. `ENV PORT` is likewise
+unused — the port in `CMD` is hardcoded.
 
 ## Architecture
 
-- **Framework:** FastAPI + Uvicorn
-- **Templates:** Inline HTML strings in Python + HTMX (WebSocket extension)
-- **Styling:** Tailwind CSS v4 — scans `app/**/*.py` for class names (configured in `resources/css/input.css` via `@source`)
-- **Data backend:** btcdata (separate service at BTCDATA_URL, default http://localhost:4100)
+- **Framework:** FastAPI
+- **Server:** Uvicorn
+- **Templates:** Inline HTML strings + HTMX (WebSocket extension)
+- **Styling:** Tailwind CSS v4
+- **Data backend:** btcdata (separate service at `BTCDATA_URL`, default `http://localhost:4100`)
 - **No database** — all data comes from btcdata
 
-### Data Flow
+### btcdata connection
+
+The browser connects only to btcprice: `ws-connect="/ws/price"` and `ws-connect="/ws/strike"`.
+Each endpoint runs `_ws_proxy`, which opens an upstream WebSocket to btcdata's `/api/price/ws`
+and `/api/strike/ws`, converts each JSON message to an HTML fragment (`price_json_to_html`,
+`strike_json_to_html`) and forwards it. `BTCDATA_URL` is the single point of contact;
+`_btcdata_ws_url` rewrites its scheme to `ws`/`wss`.
+
+## Source Layout
 
 btcprice acts as a WebSocket proxy between the browser and btcdata:
 1. Browser connects via HTMX WebSocket to `/ws/price` or `/ws/strike`