Improve documentation SEO and agent retrieval

[ayushflow]

Description

Improves site-wide SEO, accessibility, freshness governance, and AI-agent consumption for the FlutterFlow documentation.

• Normalizes metadata and accessibility across 376 source documents without treating metadata-only changes as new freshness evidence.
• Generates canonical llms.txt, llms-full.txt, bounded topic packs, page-level Markdown, an agent manifest, clean sitemap metadata, and TechArticle structured data.
• Adds copy and agent-consumption controls while loading the third-party chatbot only after interaction.
• Adds deterministic SEO and retrieval audits, CI enforcement, and scheduled freshness checks.
• Corrects and verifies high-value task and troubleshooting guidance for accurate agent answers.
• Replaces 16 oversized referenced GIFs with optimized MP4s and removes duplicate or unused media, reducing repository payload by approximately 116 MB.

Type of change

• Typo fix
• New feature
• Enhancement to current docs
• Removed outdated references
• Update assets

Validation

• npm run typecheck
• npm run build
• npm run audit:seo-agent:built
• npm run eval:agent-retrieval
• git diff --check origin/main...HEAD

Build output covers 379 canonical pages and 12 bounded topic packs. All eight static audit categories score A+ at 100%. The fixed retrieval evaluation covers 50 intents and 300 query variants with 100% top-1 accuracy, recall@5, and evidence support.

Public repository safety

The complete branch delta, final tree, and branch history were scanned before publication. No private implementation paths, private code excerpts, credentials, new secret material, symlinks, submodules, hidden payloads, or local audit reports are included.