fix: Complete mobile UX overhaul - horizontal scroll, landscape mode, and centering

Fixes three critical mobile issues across Android and iPhone:

1. HORIZONTAL SCROLL ELIMINATION (CRITICAL)
   - Added overflow-x: hidden to html and body globally
   - Landscape: Aggressive max-width: 100vw on all containers
   - Fixed .cv-page, .cv-container overflow issues
   - Prevented scale transform from causing overflow

2. LANDSCAPE MODE COMPLETE FIX
   - Single column layout enforced (grid-template-columns: 1fr)
   - Photo visible and sized appropriately (max-width: 120px)
   - Hamburger menu visible and accessible
   - Action bar simplified (center controls hidden)
   - Language selector compact
   - Smaller buttons (40px) with recalculated positions
   - Typography reduced for better fit

3. BUTTON CENTERING (VERIFIED WORKING)
   - Confirmed perfect centering in portrait mode
   - Android: 290px bar centered at viewport center (188px)
   - iPhone: Identical centering behavior
   - Landscape: 240px bar for 5 buttons (40px each)

Files modified:
- static/css/01-foundation/_reset.css - Global overflow-x fix
- static/css/05-responsive/_breakpoints.css - Comprehensive landscape overhaul
- tests/mjs/54-landscape-mode-test.mjs - Landscape validation (Android + iPhone)
- tests/mjs/55-button-centering-test.mjs - Button centering validation
- tests/mjs/56-landscape-debug-test.mjs - Media query debugging tool
- tests/mjs/57-horizontal-scroll-debug.mjs - Scroll width debugging tool

Test results:
✅ Portrait: Buttons perfectly centered (0px offset)
✅ Landscape: Single column, no horizontal scroll
✅ Hamburger visible and accessible in landscape
✅ Photo visible in all orientations
✅ Android + iPhone parity confirmed

static/css/01-foundation/_reset.css

@@ -25,13 +25,16 @@ body {
   background-image: var(--page-bg-pattern);
   background-size: 40px 40px; /* For dark theme diagonal grid */
   background-attachment: fixed;
-  overflow-x: auto;
+  max-width: 100vw; /* Prevent horizontal overflow */
+  overflow-x: hidden; /* NO horizontal scroll on mobile */
 }
 
 /* Smooth scrolling */
 html {
   scroll-behavior: smooth;
   scroll-padding-top: 70px; /* Account for fixed header */
+  max-width: 100vw; /* Prevent horizontal overflow */
+  overflow-x: hidden; /* NO horizontal scroll */
 }
 
 /* Ensure Iconify icons display properly */