Split data layer into btcdata service

Remove DB, Binance WebSocket, and Kraken pollers from btcprice.
UI now uses vanilla EventSource connecting to btcdata for live
price updates. btcprice is now a pure UI service with no database.

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

CLAUDE.md

@@ -1,15 +1,14 @@
 # btcprice
 
-Bitcoin price tracker - Clojure Kit web application.
+Bitcoin price tracker UI — Clojure Kit web application. Serves the HTML/HTMX/Tailwind UI. Connects to btcdata for live price data via SSE.
 
 ## Build & Development Commands
 
-- `make run` — Start dev server on port 3000
-- `make repl` — Start nREPL on port 7888
+- `make run` — Start dev server on port 4000
+- `make repl` — Start nREPL
 - `make test` — Run tests
 - `make tailwind` — Watch Tailwind CSS for changes
 - `make uberjar` — Build production JAR
-- `docker compose up -d` — Start PostgreSQL
 
 ## REPL Commands
 
@@ -18,10 +17,6 @@ Bitcoin price tracker - Clojure Kit web application.
 (go)          ;; Start system
 (reset)       ;; Reload code & restart
 (halt)        ;; Stop system
-(reset-db)    ;; Drop & re-migrate database
-(migrate)     ;; Run pending migrations
-(rollback)    ;; Rollback last migration
-(query-fn)    ;; Get database query function
 ```
 
 ## Architecture
@@ -29,9 +24,10 @@ Bitcoin price tracker - Clojure Kit web application.
 - **Framework:** Kit (Integrant-based)
 - **Server:** Undertow
 - **Routing:** Reitit
-- **Templates:** Hiccup + HTMX
+- **Templates:** Hiccup + vanilla JS EventSource
 - **Styling:** Tailwind CSS v4
-- **Database:** PostgreSQL + conman + Migratus
+- **Data backend:** btcdata (separate service at BTCDATA_URL, default http://localhost:4100)
+- **No database** — all data comes from btcdata
 
 ## Source Layout
 
@@ -50,6 +46,6 @@ src/clj/pmagnus/btcprice/
     │   └── formats.clj   # Content negotiation
     └── routes/
         ├── api.clj       # /api routes (JSON)
-        ├── ui.clj        # UI routes (HTML)
+        ├── ui.clj        # UI routes (HTML + EventSource)
         └── utils.clj     # Route utilities
 ```