feat(docs): Add visit tracking

[muscariello]

Summary

This PR adds a privacy-first visit tracking system for docs.agntcy.org.

Changes

Core Implementation

• Visit Tracker (docs/javascripts/visit-tracker-secure.js): Secure client-side tracking using GitHub Issues API
• GitHub Workflow (process-visits-secure.yml): Secure workflow for processing visit data using GitHub secrets
• Processing Script (process_visits.py): Python script to process and store visit data in gist

Configuration

• Updated mkdocs.yml to include tracking script
• Added visit archive directory structure

Features

✅ Privacy First

• No tokens exposed (uses public GitHub Issues API for submission)
• GitHub secrets for secure gist access (server-side only)
• Respects Do Not Track
• Disabled on localhost
• Bot detection

✅ Secure Architecture

• Client submits via GitHub Issues (no auth needed)
• GitHub Actions processes with secrets (secure)
• Data stored in private gist
• Automatic issue cleanup

✅ Developer Friendly

• Clean separation of concerns
• Well-organized in .github/
• Comprehensive inline documentation

How It Works

1. Client Side: Browser collects visits in localStorage
2. Submission: Creates GitHub Issue with JSONL data (public API, no auth)
3. Processing: GitHub Actions triggered by issue label
4. Storage: Actions uses secrets to append to gist
5. Cleanup: Issue auto-closed after processing

Security

• ✅ No tokens in client code
• ✅ GitHub secrets used only server-side
• ✅ Private gist for data storage
• ✅ Automated issue lifecycle

Related Issue

Closes #279

[muscariello]

Check this flow @ramizpolic

┌──────────────┐
│ User Browser │ (1) Submits via GitHub Issue API (no auth)
└──────┬───────┘
       │
       ↓
┌─────────────────────────────────────────┐
│ GitHub Issue                             │
│ - Public API (no token needed)          │
│ - Contains JSONL in code block          │
└──────┬──────────────────────────────────┘
       │
       ↓ (2) Trigger workflow
┌────────────────────────────────────────────┐
│ GitHub Actions Workflow                    │
│ ✓ Validates issue body                    │
│ ✓ Extracts JSONL block safely             │
│ ✓ Runs Python validation script           │
│ ✓ Checks all fields and formats           │
│ ✓ Rejects invalid data                    │
└──────┬─────────────────────────────────────┘
       │
       ↓ (3) Only if valid
┌────────────────────────────────────────────┐
│ GitHub Gist Storage (with secrets)         │
│ ✓ Appends validated data                  │
│ ✓ Uses VISIT_GIST_TOKEN (server-side)     │
│ ✓ Never exposes token to client           │
└────────────────────────────────────────────┘

[muscariello]

We keep this on hold as a user must be authenticated in github to post. This is not always true and when true it does not work for privacy issues.