Restore context_template.go from commit 82bfde2a37 which added:
- ScriptImport() — generates script tags with CSP nonces
- CspScriptNonce() — generates per-request nonces
- HeadMetaContentSecurityPolicy() — CSP meta header
- CurrentWebBanner() — web banner support
- globalVars — cached script import configuration
These methods were missing from our manual TemplateContext definition,
causing "ScriptImport is not a method" runtime template errors.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Jonathan Miller
c74a0d27e4