Complete BetterBrand public repository handoff

[daniel-techAI]

Summary

• complete the public README, contribution, support, security, change, licensing, and deployment handoff
• remove stale account-flag, store-ID, internal tooling, and single-provider claims
• turn the Shopify launch material into a truthful pre-launch gate with unresolved legal, product, payment, shipping, privacy, and fulfillment blockers
• add issue forms, a pull-request template, Theme Check configuration, and a least-privilege validation workflow
• fix preview contrast, mobile sort naming, cart naming, skip navigation, metadata, and keyboard access to the horizontal product gallery
• add desktop and Pixel 7 Playwright + axe regression coverage across all eight preview routes
• preserve and merge the latest storefront imagery correction from main

Validation

• Shopify Theme Check 4.5.2: 52 files inspected, zero offenses (previous run; rerunning in this PR)
• Playwright: 16/16 desktop and mobile preview accessibility tests pass
• axe: no serious or critical WCAG 2.2 AA violations across the eight tested routes
• no document-level horizontal overflow at desktop or mobile viewport sizes
• 16 JSON files and 22 Liquid section schemas parsed
• local Markdown/HTML links and Liquid references resolve
• no tracked secrets, .env files, store hostnames, theme IDs, ZIPs, logs, or build artifacts
• git diff --check passed

Deployment boundary

This pull request does not access Shopify, upload a theme, publish a live theme, or change store data. The repository remains explicitly pre-launch.