feat: rewrite busylight as FastAPI web application with SQLite

Replace the standalone Python script + config.cfg with a full web
application featuring:
- FastAPI backend with REST API
- SQLite database (config, state, activity log separated)
- Bootstrap 5 web interface for configuration
- Pages: Dashboard, Users, Devices, Assignments, Color Rules, Settings, Log
- APScheduler background polling for Teams presence + AIDA status
- systemd service file for Linux deployment
- Migration script to import existing config.cfg data

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

static/style.css

@@ -0,0 +1,131 @@
+:root {
+    --sidebar-width: 240px;
+}
+
+body {
+    min-height: 100vh;
+    background: #f4f6f9;
+}
+
+.sidebar {
+    width: var(--sidebar-width);
+    min-height: 100vh;
+    position: fixed;
+    top: 0;
+    left: 0;
+    z-index: 100;
+    overflow-y: auto;
+}
+
+.sidebar .nav-link {
+    padding: 0.6rem 1rem;
+    border-radius: 0.375rem;
+    margin: 2px 8px;
+    transition: background 0.15s;
+}
+
+.sidebar .nav-link:hover {
+    background: rgba(255, 255, 255, 0.1);
+}
+
+.sidebar .nav-link.active {
+    background: rgba(255, 255, 255, 0.15);
+    font-weight: 600;
+}
+
+.sidebar .nav-link i {
+    width: 24px;
+    text-align: center;
+    margin-right: 8px;
+}
+
+.main-content {
+    margin-left: var(--sidebar-width);
+    min-height: 100vh;
+    padding: 1.5rem;
+}
+
+.status-dot {
+    width: 16px;
+    height: 16px;
+    border-radius: 50%;
+    display: inline-block;
+    border: 1px solid rgba(0, 0, 0, 0.2);
+}
+
+.busylight-card {
+    border: none;
+    border-radius: 12px;
+    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
+    transition: box-shadow 0.2s;
+}
+
+.busylight-card:hover {
+    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.12);
+}
+
+.segment-bar {
+    height: 40px;
+    border-radius: 6px;
+    display: flex;
+    align-items: center;
+    padding: 0 12px;
+    color: #333;
+    font-size: 0.9rem;
+    border: 1px solid rgba(0, 0, 0, 0.1);
+}
+
+.segment-bar.empty {
+    background: repeating-linear-gradient(
+        45deg,
+        #f0f0f0,
+        #f0f0f0 5px,
+        #e8e8e8 5px,
+        #e8e8e8 10px
+    );
+    color: #999;
+    font-style: italic;
+}
+
+.color-preview {
+    width: 40px;
+    height: 40px;
+    border-radius: 8px;
+    border: 2px solid rgba(0, 0, 0, 0.15);
+    cursor: pointer;
+}
+
+.table th {
+    font-weight: 600;
+    font-size: 0.85rem;
+    text-transform: uppercase;
+    letter-spacing: 0.5px;
+    color: #6c757d;
+}
+
+.badge-online {
+    background: #28a745;
+}
+
+.badge-offline {
+    background: #6c757d;
+}
+
+.log-table {
+    font-size: 0.85rem;
+}
+
+.log-table td {
+    vertical-align: middle;
+}
+
+@media (max-width: 768px) {
+    .sidebar {
+        width: 100%;
+        min-height: auto;
+        position: relative;
+    }
+    .main-content {
+        margin-left: 0;
+    }
+}