fix: use a renderable placeholder for externalDatabase.password

The chart validates the password against ^[a-zA-Z0-9._-]+$, so the
`<password>` placeholder I added last round made the reference topology fail to
render if copied as-is. Replaced with a compliant placeholder and documented
the character restriction, which is a real constraint operators hit when
generating one.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015BwsJTEQRzWJaY4BRCkPZt

Author: waleedlatif1

apps/docs/content/docs/platform/self-hosting/scaling.mdx

@@ -147,11 +147,15 @@ externalDatabase:
   port: 6432
   database: simstudio
   sslMode: require
+  # Replace with your real password. It must match ^[a-zA-Z0-9._-]+$ — the
+  # chart rejects anything else, including the angle brackets a placeholder
+  # would normally use.
+  #
   # Required unless you use externalDatabase.existingSecret or External
-  # Secrets, either of which skips this check. Under External Secrets, map
+  # Secrets, either of which skips both checks. Under External Secrets, map
   # externalSecrets.remoteRefs.externalDatabase.password — an omitted mapping
   # renders no Secret and the pod cannot start.
-  password: "<password>"
+  password: "replace-with-your-password"
 
 autoscaling:
   enabled: true