feat(01-01): create configuration infrastructure

- AppConfig, ServerConfig, DatabaseConfig case classes
- zio-config-magnolia for automatic Config derivation
- HOCON application.conf with env variable overrides
- Server: host/port with SERVER_HOST/SERVER_PORT overrides
- Database: host/port/database/user/password with DB_* overrides

summercms/resources/application.conf

@@ -0,0 +1,19 @@
+server {
+  host = "0.0.0.0"
+  host = ${?SERVER_HOST}
+  port = 8080
+  port = ${?SERVER_PORT}
+}
+
+database {
+  host = "localhost"
+  host = ${?DB_HOST}
+  port = 5432
+  port = ${?DB_PORT}
+  database = "summercms"
+  database = ${?DB_NAME}
+  user = "summercms"
+  user = ${?DB_USER}
+  password = "summercms"
+  password = ${?DB_PASSWORD}
+}