docs: redact remaining sensitive data and fix stale service counts

- linux.md: redact sudo password from grep example
- networking.md: update nine→eleven service count in summary
- 01-what-you-need.md: redact real VPS IP from example

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

homelab-mastery/concepts/linux.md

@@ -161,7 +161,7 @@ You used this to run ufw commands non-interactively. In real production environm
 grep "error" /var/log/syslog          # lines containing "error"
 grep -i "error" logfile               # case-insensitive
 grep -n "AUTHENTIK" docker-compose.yml # show line numbers
-grep -r "p12217177" /opt/kitestacks/  # recursive search in directory
+grep -r "search-term" /opt/kitestacks/  # recursive search in directory
 ```
 
 **sed** (stream editor) modifies text: