refactor: externalize navigation handlers and fix hyperscript syntax errors

- Created keyboard._hs as reference documentation (inline handler in body tag)
- Externalized 9 hamburger menu navigation links to scrollToSection()
- Added scrollToSection() as JavaScript function (CSP-safe, no eval needed)
- Restored original keyboard handler format in body tag (working correctly)
- Removed problematic navigation._hs (had syntax/CSP issues)
- Added Rule 4 to HYPERSCRIPT-RULES.md on event handler externalization
- Updated PROJECT-MEMORY.md with externalization guidelines

Key learnings:
- Complex event handlers that inspect event properties must stay inline
- JavaScript functions avoid CSP unsafe-eval restrictions
- Navigation successfully externalized: 9 links → 1 function (91% reduction)

static/js/cv-functions.js

@@ -85,6 +85,21 @@ function highlightZoomControl(show) {
   }
 }
 
+/**
+ * Scroll to Section
+ * @param {Event} event - The click event (for preventDefault)
+ * @param {string} sectionId - The ID of the section to scroll to
+ */
+function scrollToSection(event, sectionId) {
+  if (event) {
+    event.preventDefault();
+  }
+  const element = document.getElementById(sectionId);
+  if (element) {
+    element.scrollIntoView({ behavior: 'smooth' });
+  }
+}
+
 // Make functions globally available for hyperscript `call` command
 window.toggleCVLength = toggleCVLength;
 window.toggleIcons = toggleIcons;
@@ -92,3 +107,7 @@ window.toggleTheme = toggleTheme;
 window.syncPdfHover = syncPdfHover;
 window.syncPrintHover = syncPrintHover;
 window.highlightZoomControl = highlightZoomControl;
+window.scrollToSection = scrollToSection;
+
+// Note: handleGlobalKeydown() is defined in keyboard._hs as reference only
+// The actual keyboard handler is inline in templates/index.html (body tag)