Ignore list for internal/paid plugins via PLUGIN_REPORT_IGNORE constant

[apermo]

Problem

Paid plugins (e.g. Yoast SEO Premium) and internal plugins that don't exist on wordpress.org generate "Plugin not found" errors. There's currently no way to suppress these lookups. (Relates to #14)

Solution

Add a PLUGIN_REPORT_IGNORE constant that can be defined in wp-config.php. Plugins on the list skip the wordpress.org API call entirely and show "Ignored (via config)" in the Repository column.

Configuration

Array (PHP 7.0+):

define( 'PLUGIN_REPORT_IGNORE', [
    'yoast-seo-premium',
    'my-internal-plugin',
] );

Comma-separated string (PHP 5.6 compatible):

define( 'PLUGIN_REPORT_IGNORE', 'yoast-seo-premium,my-internal-plugin' );

Behavior

• Ignored plugins still appear in the report with local data (name, author, version, activation status)
• Repository column shows "Ignored (via config)" instead of an error
• No API call or SVN check is made
• Cached with the longer TTL (CACHE_LIFETIME_NOREPO / 1 week)

[apermo]

Duplicate — this is covered by #14. PR #90 now references #14 directly.