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>

resources/system.edn

@@ -33,8 +33,8 @@
   :env    #ig/ref :system/env}
 
  :db.sql/connection
- #profile {:dev  {:jdbc-url "jdbc:postgresql://localhost:5432/btcprice?user=btcprice&password=btcprice"}
-           :test {:jdbc-url "jdbc:postgresql://localhost:5432/btcprice?user=btcprice&password=btcprice"}
+ #profile {:dev  {:jdbc-url #env JDBC_URL}
+           :test {:jdbc-url #env JDBC_URL}
            :prod {:jdbc-url #env JDBC_URL
                   :init-size     1
                   :min-idle      1