[P1] Add Last Updated Timestamp to All Documentation Pages

[flexykrn]

Bug Description

All documentation pages lack a 'Last Updated' timestamp, making it impossible for users to determine if information is current or stale. This is critical for blockchain documentation where protocols, RPC endpoints, and tooling change frequently.

Competitor Benchmark

• Ethereum: Shows 'Page last updated' on every page via mkdocs-git-revision-date plugin
• Solana: Displays modification date in page footer
• Polygon: Uses 'Last modified' indicator with git-based timestamps
• Base: Shows relative time ('Updated 3 days ago')

Affected Pages

• All 191 documentation pages in the repository
• Particularly critical for:
  • /api/json-rpc (endpoints change)
  • /xdcchain/developers/node_operators/ (setup instructions evolve)
  • /subnet/ (rapidly developing feature)
  • /smartcontract/ (tooling updates)

Blast Radius

• Primary: All documentation readers
• Secondary: Developers relying on accurate, current information
• Risk: Users following stale instructions, wasted debugging time, loss of trust

Root Cause Analysis

The documentation site is built with MkDocs but does not include the mkdocs-git-revision-date-localized-plugin or equivalent. Git history exists but is not surfaced to readers.

Proposed Solution

Option A: MkDocs Plugin (Recommended)

Install and configure mkdocs-git-revision-date-localized-plugin:

# mkdocs.yml
plugins:
  - git-revision-date-localized:
      type: datetime
      fallback_to_build_date: true
      enable_creation_date: true

Option B: Manual Frontmatter

Add last_updated field to each page's YAML frontmatter.

Additional Fixes Required

• Add plugin to requirements.txt
• Update mkdocs.yml configuration
• Verify CI/CD has git history available
• Style timestamp in CSS (subtle, non-intrusive)

Acceptance Criteria

• Every page displays 'Last updated: [date]' in footer or header
• Date format is localized
• Fallback works if git history unavailable
• Mobile responsive placement
• Does not interfere with existing page layout

Raw Context

Users currently have no way to know if a guide from 2023 still works in 2025. This undermines confidence in all documentation.