Accessibility fixes and form session expiration fix

- Fix color contrast: change #179e83 to #148069 for WCAG AA compliance
- Add ARIA attributes to mobile nav toggle (aria-expanded, aria-controls)
- Implement focus trap on mobile menu with Escape key support
- Add aria-hidden to decorative hero SVG
- Add ARIA validation to contact form (aria-invalid, aria-describedby)
- Fix touch target sizes (notification close button 48x48px)
- Fix form session expiration by relaxing timestamp validation
- Add cache busting (v1.1.0) to JS/CSS files
- Update service worker cache version to force refresh

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

assets/css/main.css

@@ -45,7 +45,7 @@ body {
 }
 
 .btn-primary {
-    background: #179e83;
+    background: #148069;
     color: white !important;
     text-decoration: none !important;
 }
@@ -152,7 +152,7 @@ body {
 }
 
 .nav-link.cta-button {
-    background: #179e83;
+    background: #148069;
     color: white;
     padding: 10px 20px;
     border-radius: 6px;
@@ -169,6 +169,13 @@ body {
     display: none;
     flex-direction: column;
     cursor: pointer;
+    background: none;
+    border: none;
+    padding: 8px;
+    min-width: 48px;
+    min-height: 48px;
+    justify-content: center;
+    align-items: center;
 }
 
 .bar {
@@ -454,7 +461,7 @@ body {
 }
 
 .step-number {
-    background: #179e83;
+    background: #148069;
     color: white;
     width: 60px;
     height: 60px;
@@ -630,6 +637,33 @@ body {
     min-height: 120px;
 }
 
+/* Form validation states */
+.form-group input[aria-invalid="true"],
+.form-group select[aria-invalid="true"],
+.form-group textarea[aria-invalid="true"] {
+    border-color: #dc2626;
+    box-shadow: 0 0 0 3px rgba(220, 38, 38, 0.1);
+}
+
+.form-group input[aria-invalid="true"]:focus,
+.form-group select[aria-invalid="true"]:focus,
+.form-group textarea[aria-invalid="true"]:focus {
+    border-color: #dc2626;
+    box-shadow: 0 0 0 3px rgba(220, 38, 38, 0.2);
+}
+
+.form-error {
+    display: block;
+    color: #dc2626;
+    font-size: 0.875rem;
+    margin-top: 6px;
+    min-height: 1.25rem;
+}
+
+.form-error:empty {
+    display: none;
+}
+
 /* Footer */
 .footer {
     background: #151f25;
@@ -1613,7 +1647,7 @@ textarea:focus-visible {
 
 /* Category link styles */
 .category-link {
-    background: #179e83;
+    background: #148069;
     color: white !important;
     padding: 5px 12px;
     border-radius: 15px;
@@ -1688,12 +1722,15 @@ textarea:focus-visible {
     color: white;
     font-size: 18px;
     cursor: pointer;
-    padding: 0;
-    width: 20px;
-    height: 20px;
+    padding: 12px;
+    width: 48px;
+    height: 48px;
+    min-width: 48px;
+    min-height: 48px;
     display: flex;
     align-items: center;
     justify-content: center;
+    margin: -12px -12px -12px 0;
 }
 
 /* Scroll to top button */
@@ -3637,7 +3674,7 @@ main {
 
 /* CSS Variables for Brand Consistency */
 :root {
-    --color-primary: #179e83;
+    --color-primary: #148069;
     --color-primary-dark: #11725e;
     --color-secondary: #144784;
     --color-secondary-light: #1a5a9e;