Add docker-compose, README, fix SSE dispatch

Use Undertow dispatch for SSE handler to avoid Ring adapter conflict.
Add docker-compose.yml (port 4101 to coexist with local dev on 4100).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -8,6 +8,16 @@ Bitcoin data backend — Clojure Kit application. Fetches BTC prices from Binanc
 - `make repl` — Start nREPL
 - `make test` — Run tests
 - `make uberjar` — Build production JAR
+- `docker compose up -d` — Start btcdata container
+
+## Docker
+
+Docker runs alongside local dev on different ports and databases:
+
+| | Local dev      | Docker         |
+|--|----------------|----------------|
+| **Port** | localhost:4100 | localhost:4101 |
+| **Database** | btcprice | btcprod |
 
 ## REPL Commands