Add pre-commit hooks for code quality and fix all lint violations

Introduces pre-commit framework with hooks for:
- General file hygiene (trailing whitespace, EOF, large files)
- Secret detection (TruffleHog)
- YAML linting (yamllint)
- Ansible linting (ansible-lint)
- Python linting/formatting (ruff)
- Shell script analysis (shellcheck, shfmt)
- TOML formatting (taplo)
- JSON formatting (prettier)

Fixes 91+ ansible-lint violations:
- Renamed variables to use role prefixes (e.g., brew_start -> alloy_brew_start)
- Capitalized handler names per convention
- Added changed_when to command tasks
- Fixed template usage in task names

Fixes shellcheck warnings:
- Removed unused variables
- Fixed SC2155 (declare and assign separately)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

ansible/roles/prometheus/tasks/main.yml

@@ -9,17 +9,17 @@
     src: prometheus.yml.j2
     dest: /opt/homebrew/etc/prometheus.yml
     mode: '0644'
-  notify: restart prometheus
+  notify: Restart prometheus
 
 - name: Configure prometheus.args
   ansible.builtin.template:
     src: prometheus.args.j2
     dest: /opt/homebrew/etc/prometheus.args
     mode: '0644'
-  notify: restart prometheus
+  notify: Restart prometheus
 
 - name: Ensure prometheus service is started
   ansible.builtin.command: brew services start prometheus
-  register: brew_start
-  changed_when: "'Successfully started' in brew_start.stdout"
+  register: prometheus_brew_start
+  changed_when: "'Successfully started' in prometheus_brew_start.stdout"
   failed_when: false