fix(smtp): inject SMTP password secret via entrypoint, not *_FILE

The official discourse/discourse image has no *_FILE support, so
DISCOURSE_SMTP_PASSWORD_FILE was silently ignored and SMTP auth booted
without a password. Read the secret in the wrapper entrypoint and export
DISCOURSE_SMTP_PASSWORD, mirroring the DB password handling. Bump
APP_ENTRYPOINT_VERSION so the new entrypoint config redeploys.

Add release notes for the bitnami->official SMTP env var renames.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

compose.smtpauth.yml

@@ -3,8 +3,8 @@ version: "3.8"
 
 services:
   app:
-    environment:
-      - DISCOURSE_SMTP_PASSWORD_FILE=/var/run/secrets/smtp_password
+    # the wrapper entrypoint reads /run/secrets/smtp_password and exports
+    # DISCOURSE_SMTP_PASSWORD (the official image has no *_FILE support)
     secrets:
       - smtp_password