v2.1.0 - Device Sync Fix & Above-Fold CRO Signals

Fixes

• Device/browser data not reaching Supabase - the enrichment sync SELECT was failing silently with Unknown column 'lcp_ms' (and time_on_page_sec, referrer, utm_*) on existing installations where ALTER TABLE migrations had never run. Added explicit per-column ALTER TABLE guards for all missing columns and added them to the CREATE TABLE SQL so dbDelta() handles both fresh installs and upgrades.
• Version bump to 2.1.0 triggers create_tables() automatically on the next admin page load via the version-check in conversioniq_init() - no deactivation/reactivation needed.
• Enrichment sync error visibility - wpdb->last_error is now logged alongside the sessions count so SQL failures appear in the debug log instead of silently showing local sessions found = 0.

Improvements

• JS tracker measureAboveFold() expanded from 4 to 9 element types: added nav_cta, trust_badge, testimonial, pricing, and progress indicators.
• AI audit context now queries the last 30 real browser sessions per page URL and appends a [BROWSER-CONFIRMED] block with per-element presence percentages.
• AI prompt updated to treat [BROWSER-CONFIRMED] signals as primary evidence for visual CRO checks (H1, CTA, hero image, trust badges, etc.), falling back to HTML-only analysis when no browser data exists.