fix(security): harden encryption key permissions, increase password minimum, remove sensitive logs (#323)

Self-heal encryption key file permissions to 0600 on startup. Increase
minimum password length from 6 to 8 characters per NIST SP 800-63B.
Remove console.log statements that exposed file paths, .env locations,
stack names, and admin usernames to stdout.

docker-entrypoint.sh

@@ -24,6 +24,8 @@ if [ "$(id -u)" = '0' ]; then
     mkdir -p "$DATA_DIR"
     find "$DATA_DIR" \( \! -user sencho -o \! -group sencho \) \
         -exec chown sencho:sencho '{}' +
+    # Restrict encryption key to owner-only access (rw-------)
+    [ -f "$DATA_DIR/encryption.key" ] && chmod 600 "$DATA_DIR/encryption.key"
     echo "[entrypoint] Data directory ownership ensured: $DATA_DIR"
 
     # 2. Fix Docker socket group access.