chore: use elxir env reading patterns

Author: decebal

apps/query-service/config/prod.exs

@@ -1,24 +1,26 @@
 import Config
 
+# Mark this as production environment (used by application.ex to skip repo if no DATABASE_URL)
+config :query_service_ex, env: :prod
+
 # For production, don't forget to configure the url host
 # to something meaningful, Phoenix uses this information
 # when generating URLs.
-
+# Note: secret_key_base is set in runtime.exs, using a build-time placeholder here
 config :query_service_ex, QueryServiceExWeb.Endpoint,
-  url: [host: System.get_env("PHX_HOST") || "localhost", port: 443, scheme: "https"],
+  url: [host: "localhost", port: 443, scheme: "https"],
   http: [
     # Enable IPv6 and bind on all interfaces.
-    # Set it to  {0, 0, 0, 0, 0, 0, 0, 1} for local network only access.
     ip: {0, 0, 0, 0, 0, 0, 0, 0},
-    port: String.to_integer(System.get_env("PORT") || "3902")
+    port: 3902
   ],
-  secret_key_base: System.fetch_env!("SECRET_KEY_BASE"),
+  secret_key_base: "build_time_placeholder_will_be_replaced_at_runtime_by_runtime_exs_config",
   server: true
 
-# Configure Rust Core backend
+# Configure Rust Core backend (defaults, can be overridden in runtime.exs)
 config :query_service_ex,
-  rust_core_url: System.get_env("RUST_CORE_URL") || "http://localhost:3900",
-  core_ws_url: System.get_env("CORE_WS_URL") || "ws://localhost:3900"
+  rust_core_url: "http://localhost:3900",
+  core_ws_url: "ws://localhost:3900"
 
 # Do not print debug messages in production
 config :logger, level: :info

apps/query-service/lib/query_service_ex/application.ex

@@ -15,14 +15,17 @@ defmodule QueryServiceEx.Application do
     # Initialize ETS cache for projections
     ProjectionSync.init_cache()
 
-    # In test mode, the Repo is started manually by test_helper.exs after testcontainers
-    # sets up the database. In other environments, the Repo starts with the application.
-    repo_children =
-      if Application.get_env(:query_service_ex, :skip_repo_start, false) do
-        []
-      else
-        [QueryServiceEx.Repo]
-      end
+    # Skip Repo start if:
+    # 1. Explicitly disabled via config (test mode with testcontainers)
+    # 2. In prod without DATABASE_URL (container health checks, image testing)
+    is_prod? = Application.get_env(:query_service_ex, :env) == :prod
+    no_database_url? = is_nil(System.get_env("DATABASE_URL"))
+
+    skip_repo? =
+      Application.get_env(:query_service_ex, :skip_repo_start, false) ||
+        (is_prod? and no_database_url?)
+
+    repo_children = if skip_repo?, do: [], else: [QueryServiceEx.Repo]
 
     children =
       repo_children ++