Add licensing system for ISP customers

- Add license.php with tiered licensing (Trial, Basic, Professional, Enterprise)
- Add license_info table to database schema
- Add license management UI to settings (License tab)
- Add license status, activation, and usage API endpoints
- Add entry and user limit enforcement based on license tier
- Add feature flags for webhooks, IP enrichment, whitelabel, PTR records
- Update README with licensing documentation and customer deployment guide

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

database/schema.sql

@@ -214,3 +214,20 @@ ALTER TABLE geofeed_entries ADD COLUMN IF NOT EXISTS flag_threat TINYINT(1) DEFA
 ALTER TABLE geofeed_entries ADD INDEX IF NOT EXISTS idx_sort_order (sort_order);
 ALTER TABLE geofeed_entries ADD INDEX IF NOT EXISTS idx_isp (ipr_isp);
 ALTER TABLE geofeed_entries ADD INDEX IF NOT EXISTS idx_asn (ipr_asn);
+
+-- License information table
+CREATE TABLE IF NOT EXISTS license_info (
+    id INT AUTO_INCREMENT PRIMARY KEY,
+    license_key VARCHAR(64) NOT NULL,
+    licensee_name VARCHAR(255) NOT NULL,
+    licensee_email VARCHAR(255) NOT NULL,
+    license_type ENUM('trial', 'basic', 'professional', 'enterprise') DEFAULT 'trial',
+    max_entries INT DEFAULT 100,
+    max_users INT DEFAULT 3,
+    features JSON DEFAULT NULL,
+    issued_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    expires_at TIMESTAMP NULL,
+    last_validated_at TIMESTAMP NULL,
+    is_active TINYINT(1) DEFAULT 1,
+    UNIQUE KEY unique_license (license_key)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;