Add admin notice when WC version exceeds PPOM tested version

Problem

PPOM doesn't warn users when they're running an untested WC version. Users experience cart/checkout issues after WC updates and churn silently — 16 users with 25 combined years of tenure left in one month without contacting support.

Solution

Add ppom_health_check_notices() to admin_notices hook. Compares WC_VERSION against PPOM's WC tested up to header. Shows dismissible warning with support link when mismatch detected.

Files Affected

• inc/admin.php — new ppom_health_check_notices() function
• classes/plugin.class.php — hook registration

Acceptance Criteria

• Notice appears when WC version > tested-up-to
• Notice does NOT appear when WC version <= tested-up-to
• Notice is dismissible
• Only shown to users with manage_woocommerce capability

Priority: Critical — prevents silent churn
Regression risk: Isolated — admin-only, no frontend impact

Start in inc/admin.php and inspect the existing admin notice patterns, then check classes/plugin.class.php for hook registration. Verify the version comparison against the plugin header and WooCommerce version, and confirm the notice is dismissible and restricted to users with manage_woocommerce capability.