fix: resolve markdownlint errors

Disable MD060 (table column alignment) and MD032 (list blank lines).
Add language tags to bare fenced code blocks (MD040).

topics/ansible-roles.md

@@ -4,7 +4,7 @@
 
 ## Role Directory Structure
 
-```
+```text
 roles/
 └── nginx/
     ├── defaults/
@@ -164,7 +164,7 @@ nginx_access_log: /var/log/nginx/access.log
 
 ## Project Layout with Roles
 
-```
+```text
 ansible-project/
 ├── ansible.cfg
 ├── site.yml                    # Master playbook

topics/ansible-variables.md

@@ -6,7 +6,7 @@
 
 Ansible merges variables from many sources. **Higher number wins.**
 
-```
+```text
  1. command line values (for constants, not variables)
  2. role defaults          (roles/x/defaults/main.yml)
  3. inventory file or script group vars

topics/systemd.md

@@ -246,7 +246,7 @@ systemctl list-timers
 
 ### OnCalendar Syntax
 
-```
+```text
 # Format: DayOfWeek Year-Month-Day Hour:Minute:Second
 
 *-*-* 02:00:00              # daily at 2am