feat: add shared templates and static assets infrastructure

Add shared template infrastructure and static assets:
- Shared Jinja2 templates for reusable components
- Favicon for branding
- Local Tailwind CSS fallback
- Shop CSS styles directory

This provides the foundation for consistent UI components across
admin, vendor, and shop frontends with CDN fallback support.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/templates/shared/cdn-fallback.html

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+{# app/templates/shared/cdn-fallback.html #}
+{# CDN with Local Fallback Pattern #}
+{# This partial handles loading CDN resources with automatic fallback to local copies #}
+
+{# Tailwind CSS with fallback #}
+<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/tailwindcss@2.2.19/dist/tailwind.min.css"
+      onerror="this.onerror=null; this.href='{{ url_for('static', path='shared/css/tailwind.min.css') }}';">
+
+{# Alpine.js with fallback - must be loaded at the end of body #}
+{# Usage: Include this partial at the bottom of your template, before page-specific scripts #}
+<script>
+// Alpine.js CDN with fallback
+(function() {
+    var script = document.createElement('script');
+    script.defer = true;
+    script.src = 'https://cdn.jsdelivr.net/npm/alpinejs@3.13.3/dist/cdn.min.js';
+
+    script.onerror = function() {
+        console.warn('Alpine.js CDN failed, loading local copy...');
+        var fallbackScript = document.createElement('script');
+        fallbackScript.defer = true;
+        fallbackScript.src = '{{ url_for("static", path="shared/js/vendor/alpine.min.js") }}';
+        document.head.appendChild(fallbackScript);
+    };
+
+    document.head.appendChild(script);
+})();
+</script>

static/shop/css/shop.css

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+/* Shop Frontend Styles */
+/* Uses CSS variables injected by theme system */
+
+/* Base Utilities */
+.hover\:text-primary:hover {
+    color: var(--color-primary) !important;
+}
+
+.text-primary {
+    color: var(--color-primary);
+}
+
+.bg-primary {
+    background-color: var(--color-primary);
+}
+
+.bg-accent {
+    background-color: var(--color-accent);
+}
+
+.border-primary {
+    border-color: var(--color-primary);
+}
+
+/* Button Styles */
+.btn-primary {
+    background-color: var(--color-primary);
+    color: white;
+    padding: 0.5rem 1rem;
+    border-radius: 0.375rem;
+    font-weight: 500;
+    transition: all 0.2s;
+}
+
+.btn-primary:hover {
+    opacity: 0.9;
+    transform: translateY(-1px);
+}
+
+.btn-secondary {
+    background-color: var(--color-secondary);
+    color: white;
+    padding: 0.5rem 1rem;
+    border-radius: 0.375rem;
+    font-weight: 500;
+    transition: all 0.2s;
+}
+
+.btn-secondary:hover {
+    opacity: 0.9;
+}
+
+.btn-outline {
+    border: 2px solid var(--color-primary);
+    color: var(--color-primary);
+    background-color: transparent;
+    padding: 0.5rem 1rem;
+    border-radius: 0.375rem;
+    font-weight: 500;
+    transition: all 0.2s;
+}
+
+.btn-outline:hover {
+    background-color: var(--color-primary);
+    color: white;
+}
+
+/* Product Card Styles */
+.product-card {
+    background: white;
+    border-radius: 0.5rem;
+    overflow: hidden;
+    transition: all 0.3s;
+    border: 1px solid var(--color-border);
+}
+
+.product-card:hover {
+    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
+    transform: translateY(-4px);
+}
+
+.product-card.dark {
+    background: #1f2937;
+    border-color: #374151;
+}
+
+.product-card-image {
+    width: 100%;
+    height: 250px;
+    object-fit: cover;
+}
+
+.product-card-title {
+    font-family: var(--font-heading);
+    font-size: 1.125rem;
+    font-weight: 600;
+    color: var(--color-text);
+    margin-bottom: 0.5rem;
+}
+
+.product-card-price {
+    font-size: 1.25rem;
+    font-weight: 700;
+    color: var(--color-primary);
+}
+
+/* Category Badge */
+.category-badge {
+    display: inline-block;
+    padding: 0.25rem 0.75rem;
+    background-color: var(--color-secondary);
+    color: white;
+    font-size: 0.75rem;
+    font-weight: 500;
+    border-radius: 9999px;
+}
+
+/* Toast Notifications */
+.toast {
+    animation: slideInRight 0.3s ease-out;
+}
+
+@keyframes slideInRight {
+    from {
+        transform: translateX(100%);
+        opacity: 0;
+    }
+    to {
+        transform: translateX(0);
+        opacity: 1;
+    }
+}
+
+/* Loading Spinner */
+.spinner {
+    border: 3px solid rgba(0, 0, 0, 0.1);
+    border-left-color: var(--color-primary);
+    border-radius: 50%;
+    width: 40px;
+    height: 40px;
+    animation: spin 1s linear infinite;
+}
+
+@keyframes spin {
+    to {
+        transform: rotate(360deg);
+    }
+}
+
+/* Search Overlay */
+.search-overlay {
+    backdrop-filter: blur(4px);
+}
+
+/* Mobile Menu Slide */
+.mobile-menu {
+    transform: translateX(-100%);
+    transition: transform 0.3s ease-out;
+}
+
+.mobile-menu.open {
+    transform: translateX(0);
+}
+
+/* Cart Badge */
+.cart-badge {
+    min-width: 1.25rem;
+    height: 1.25rem;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    font-size: 0.75rem;
+}
+
+/* Smooth Transitions */
+* {
+    transition-property: background-color, border-color, color, fill, stroke;
+    transition-timing-function: cubic-bezier(0.4, 0, 0.2, 1);
+    transition-duration: 150ms;
+}
+
+/* Typography with Theme Fonts */
+h1, h2, h3, h4, h5, h6 {
+    font-family: var(--font-heading);
+}
+
+body {
+    font-family: var(--font-body);
+    color: var(--color-text);
+    background-color: var(--color-background);
+}
+
+/* Dark Mode Adjustments */
+.dark body {
+    background-color: #111827;
+    color: #f9fafb;
+}
+
+.dark .product-card {
+    background-color: #1f2937;
+    border-color: #374151;
+}
+
+.dark .product-card-title {
+    color: #f9fafb;
+}
+
+/* Hero Section */
+.hero-section {
+    background: linear-gradient(135deg, var(--color-primary), var(--color-secondary));
+    color: white;
+    padding: 4rem 2rem;
+    text-align: center;
+}
+
+/* Feature Cards */
+.feature-card {
+    padding: 2rem;
+    border-radius: 0.5rem;
+    border: 1px solid var(--color-border);
+    transition: all 0.3s;
+}
+
+.feature-card:hover {
+    border-color: var(--color-primary);
+    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
+}
+
+/* Breadcrumbs */
+.breadcrumb {
+    display: flex;
+    gap: 0.5rem;
+    align-items: center;
+    font-size: 0.875rem;
+    color: #6b7280;
+}
+
+.breadcrumb a:hover {
+    color: var(--color-primary);
+}
+
+/* Price Display */
+.price-old {
+    text-decoration: line-through;
+    color: #9ca3af;
+    font-size: 0.875rem;
+}
+
+.price-new {
+    color: var(--color-accent);
+    font-weight: 700;
+    font-size: 1.5rem;
+}
+
+.price-discount {
+    background-color: var(--color-accent);
+    color: white;
+    padding: 0.25rem 0.5rem;
+    border-radius: 0.25rem;
+    font-size: 0.75rem;
+    font-weight: 600;
+}
+
+/* Rating Stars */
+.rating-stars {
+    display: flex;
+    gap: 0.125rem;
+    color: #fbbf24;
+}
+
+/* Responsive Grid */
+.product-grid {
+    display: grid;
+    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
+    gap: 1.5rem;
+}
+
+@media (max-width: 640px) {
+    .product-grid {
+        grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
+        gap: 1rem;
+    }
+}