fix: add REDIS_PASSWORD support to runtime configuration

Redis authentication was failing with "NOAUTH Authentication required"
because the password wasn't being read from the environment variable.

Changes:
- Read REDIS_PASSWORD from environment in runtime.exs
- Add password to :redis config keyword list if present
- Phoenix.PubSub.Redis and Exq now read password from Application config

The application.ex and exq_supervisor.ex already had password support
from System.get_env("REDIS_PASSWORD"), but runtime.exs wasn't passing
the password through to the :redis config, so it was never available
to the application code.

This enables connection to the new Proxmox-hosted Valkey instance at
10.0.15.21 with authentication.

config/runtime.exs

@@ -49,6 +49,19 @@ if config_env() == :prod do
   # Configure Redis/Valkey connection
   redis_host = System.get_env("REDIS_HOST") || "localhost"
   redis_port = String.to_integer(System.get_env("REDIS_PORT") || "6379")
+  redis_password = System.get_env("REDIS_PASSWORD")
+
+  redis_config = [
+    host: redis_host,
+    port: redis_port
+  ]
+
+  redis_config =
+    if redis_password do
+      Keyword.put(redis_config, :password, redis_password)
+    else
+      redis_config
+    end
 
   config :libcluster,
     topologies: [
@@ -153,8 +166,5 @@ if config_env() == :prod do
 
   # Set default sender for all emails
   config :towerops, :mailer_from, {"Towerops", "hi@towerops.net"}
-
-  config :towerops, :redis,
-    host: redis_host,
-    port: redis_port
+  config :towerops, :redis, redis_config
 end