Use .env for database config, upgrade integrant/repl to 0.5.0

Load .env vars via Makefile, use #env JDBC_URL for all profiles in
system.edn, switch ig/prep to ig/expand, and add missing namespace
requires in core.clj to match elprice project conventions.

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

env/dev/clj/user.clj

@@ -3,19 +3,21 @@
    [clojure.tools.logging :as log]
    [integrant.core :as ig]
    [integrant.repl :refer [go halt reset reset-all set-prep!]]
-   [pmagnus.btcprice.config :as config]))
+   [integrant.repl.state :as state]
+   [pmagnus.btcprice.config :as config]
+   [pmagnus.btcprice.core]))
 
 (defn dev-prep! []
   (set-prep!
    (fn []
      (-> (config/system-config {:profile :dev})
-         (ig/prep)))))
+         (ig/expand)))))
 
 (defn test-prep! []
   (set-prep!
    (fn []
      (-> (config/system-config {:profile :test})
-         (ig/prep)))))
+         (ig/expand)))))
 
 (defn reset-db []
   (let [sys (or @pmagnus.btcprice.core/system