fix: Mobile hamburger menu and iPad sidebar visibility

Mobile fixes:
- Add click toggle handler for hamburger menu (was hover-only)
- Menu now opens/closes on tap and closes when clicking outside
- Keep hover support for desktop

iPad fixes:
- Sidebar content now visible on touch devices (901-1280px)
- Added (hover: hover) media query to prevent hide-on-hover on tablets

Security improvements:
- Replace exec.CommandContext with go-git library for git operations
- Add path traversal and command injection prevention
- Fix race condition in template hot reload
- Add environment-based cookie Secure flag

Code quality:
- Add constants.go for magic numbers
- Remove unused code (ParsePreferenceToggleRequest, DomainError)
- Add FOUC prevention with inline critical CSS
- Add Makefile dev/run/clean targets
- Fix README git clone URL
- Add doc/DECISIONS.md for architectural decisions

Tests:
- Add hamburger menu click toggle tests
- Add iPad sidebar visibility tests
- Update security tests for go-git implementation
- Add cookie Secure flag tests

static/css/05-responsive/_breakpoints.css

@@ -104,11 +104,20 @@
         gap: 0.5rem;
     }
 
+}
+
+/* ========================================
+   Sidebar Hide-on-Hover: ONLY for devices with hover support
+   Prevents hiding on iPad/tablets where hover doesn't work
+   ======================================== */
+@media (min-width: 901px) and (max-width: 1280px) and (hover: hover) {
     /* ========== Sidebar Content - Hide Text, Show on Hover ========== */
+    /* Only apply on devices that support hover (not touch devices) */
     .sidebar-content {
         max-height: 0 !important;
         overflow: hidden !important;
         opacity: 0 !important;
+        transition: max-height 0.3s ease, opacity 0.3s ease;
     }
 
     /* Show sidebar content on hover */
@@ -221,21 +230,6 @@
         padding: 0.65rem 1.5rem;
         gap: 0.5rem;
     }
-
-    /* ========== Sidebar Content - Hide Text, Show on Hover ========== */
-    .sidebar-content {
-        max-height: 0 !important;
-        overflow: hidden !important;
-        opacity: 0 !important;
-    }
-
-    /* Show sidebar content on hover */
-    .skill-category:hover .sidebar-content,
-    .cv-sidebar-section:hover .sidebar-content {
-        max-height: 1000px !important;
-        opacity: 1 !important;
-        margin-top: 10px !important;
-    }
 }
 
 /* ========================================