Refactor template JavaScript into static assets

[itsDNNS]

Summary

• move dashboard, setup, settings, and connection-monitor behavior from executable template scripts into versioned static JavaScript assets
• pass server data through inert application/json bootstrap blocks with validated browser-side contracts
• add native Node 22 tests for bootstrap, URL, state, formatting, and service-worker policy behavior
• preserve path-prefix routing and offline/PWA behavior without injecting executable inline JavaScript
• add the pinned Node CI job and contributor test instructions

Verification

• npm ci && npm test (9 passed)
• python -m pytest tests/ -q --tb=short --ignore=tests/e2e (3730 passed, 2 skipped)
• selected Chromium E2E for setup, settings, connection monitor, PWA, path prefixes, security, and mobile quality (170 passed)
• 34 templates scanned with zero executable inline script bodies
• browser runtime audit of dashboard, settings, and mobile setup with no page, console, or request errors
• python scripts/i18n_check.py --validate (69 languages)

Tracking: https://github.com/itsDNNS/docsight-optimization-offensive/issues/3