Split monolithic index.html and style.css for maintainability

- Extract 15 modals and 3 partials from index.html into Jinja2 templates
  (templates/modals/*.html, templates/partials/*.html)
- Split style.css (3,712 lines) into 11 feature-scoped CSS files under
  static/css/ (base, layout, components, cards, modal, calibration,
  dashboard, streams, patterns, profiles, tutorials)
- Switch root route from FileResponse to Jinja2Templates
- Add jinja2 dependency
- Consolidate duplicate @keyframes spin definition
- Browser receives identical assembled HTML — zero JS changes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/static/css/layout.css

@@ -0,0 +1,209 @@
+header {
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    padding: 20px 0 10px;
+    margin-bottom: 10px;
+    position: relative;
+    z-index: 2100;
+}
+
+.header-title {
+    display: flex;
+    align-items: center;
+    gap: 10px;
+}
+
+h1 {
+    font-size: 2rem;
+    color: var(--primary-color);
+}
+
+h2 {
+    margin-bottom: 20px;
+    color: var(--text-color);
+    font-size: 1.5rem;
+}
+
+.server-info {
+    display: flex;
+    align-items: center;
+    gap: 15px;
+}
+
+.header-link {
+    color: var(--text-secondary);
+    text-decoration: none;
+    font-size: 0.85rem;
+    font-weight: 500;
+    padding: 4px 8px;
+    border-radius: 4px;
+    transition: color 0.2s, background 0.2s;
+}
+
+.header-link:hover {
+    color: var(--text-color);
+    background: var(--bg-secondary);
+}
+
+#server-version {
+    font-size: 0.75rem;
+    font-weight: 400;
+    color: var(--text-secondary);
+    background: var(--border-color);
+    padding: 2px 8px;
+    border-radius: 10px;
+    letter-spacing: 0.03em;
+}
+
+.status-badge {
+    font-size: 1.5rem;
+    animation: pulse 2s infinite;
+}
+
+.status-badge.online {
+    color: var(--primary-color);
+}
+
+.status-badge.offline {
+    color: var(--danger-color);
+}
+
+@keyframes pulse {
+    0%, 100% { opacity: 1; }
+    50% { opacity: 0.5; }
+}
+
+/* WLED device health indicator */
+.health-dot {
+    display: inline-block;
+    width: 10px;
+    height: 10px;
+    border-radius: 50%;
+    margin-right: 8px;
+    vertical-align: middle;
+    flex-shrink: 0;
+}
+
+.health-dot.health-online {
+    background-color: #4CAF50;
+    box-shadow: 0 0 6px rgba(76, 175, 80, 0.6);
+}
+
+.health-dot.health-offline {
+    background-color: var(--danger-color);
+    box-shadow: 0 0 6px rgba(244, 67, 54, 0.6);
+}
+
+.health-dot.health-unknown {
+    background-color: #9E9E9E;
+    animation: pulse 2s infinite;
+}
+
+.health-latency {
+    font-size: 0.7rem;
+    font-weight: 400;
+    color: #4CAF50;
+    margin-left: auto;
+    padding-left: 8px;
+    opacity: 0.85;
+}
+
+.health-latency.offline {
+    color: var(--danger-color);
+}
+
+/* Tabs */
+.tab-bar {
+    display: flex;
+    align-items: center;
+    gap: 4px;
+    border-bottom: 2px solid var(--border-color);
+    margin-bottom: 16px;
+}
+
+.tab-btn {
+    background: none;
+    border: none;
+    padding: 10px 18px;
+    font-size: 1rem;
+    font-weight: 500;
+    color: var(--text-secondary);
+    cursor: pointer;
+    border-bottom: 2px solid transparent;
+    margin-bottom: -2px;
+    transition: color 0.2s, border-color 0.2s;
+}
+
+.tab-btn:hover {
+    color: var(--text-color);
+}
+
+.tab-btn.active {
+    color: var(--primary-color);
+    border-bottom-color: var(--primary-color);
+}
+
+.tab-panel {
+    display: none;
+}
+
+.tab-panel.active {
+    display: block;
+}
+
+/* Theme Toggle */
+.theme-toggle {
+    background: var(--card-bg);
+    border: 1px solid var(--border-color);
+    padding: 6px 12px;
+    border-radius: 4px;
+    cursor: pointer;
+    font-size: 1.2rem;
+    transition: transform 0.2s;
+    margin-left: 10px;
+}
+
+.theme-toggle:hover {
+    transform: scale(1.1);
+}
+
+/* Footer */
+.app-footer {
+    margin-top: 20px;
+    padding: 15px 0;
+    text-align: center;
+}
+
+.footer-content {
+    color: var(--text-secondary);
+    font-size: 0.9rem;
+}
+
+.footer-content p {
+    margin: 0;
+}
+
+
+.footer-content strong {
+    color: var(--text-color);
+}
+
+.footer-content a {
+    color: var(--primary-color);
+    text-decoration: none;
+    transition: opacity 0.2s;
+}
+
+.footer-content a:hover {
+    opacity: 0.8;
+    text-decoration: underline;
+}
+
+@media (max-width: 768px) {
+    header {
+        flex-direction: column;
+        gap: 15px;
+        text-align: center;
+    }
+}