fix: Improve BIND9 9.20 molecule scenario testing

- Add dnsutils and bind9-doc installation in prepare.yml
  Ensures dig command and documentation are available for testing

- Enhance verify.yml with improved validation:
  - Add named-checkconf syntax validation
  - Improve error detection logic in BIND logs
  - Add explicit error check assertions
  - Increase log tail output from 20 to 30 lines for better diagnostics

These fixes address PR #14 review issues #3, #4, and #5:
- Issue #3: Molecule converge.yml configuration (valid, no changes needed)
- Issue #4: prepare.yml now installs required testing tools
- Issue #5: verify.yml now includes better validation and error checking

Related to: PR #14

molecule/bind9-20/prepare.yml

@@ -5,3 +5,10 @@
     - name: Update package cache
       ansible.builtin.apt:
         update_cache: true
+
+    - name: Install DNS query tools (dnsutils)
+      ansible.builtin.apt:
+        name:
+          - dnsutils
+          - bind9-doc
+        state: present