Replace local Docker PostgreSQL with external DB via .env

Remove docker-compose.yml and use JDBC_URL from .env for all
profiles. Makefile now exports .env variables automatically.

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

resources/system.edn

@@ -47,8 +47,8 @@
   :env #ig/ref :system/env}
 
  :db.sql/connection
- #profile {:dev {:jdbc-url "jdbc:postgresql://localhost:5432/elprice?user=elprice&password=elprice"}
-           :test {:jdbc-url "jdbc:postgresql://localhost:5432/elprice?user=elprice&password=elprice"}
+ #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