fix(docs): link footer to Tangle home - #186

Changed pages include:

• index.html - view
• 404.html - view
• ai.html - view
• blueprints.html - view
• gateway.html - view
• intelligence.html - view
• platform.html - view
• release-notes.html - view
• sandbox.html - view
• blueprint-agent/integrations.html - view

There are more changes not included in the list