feat(dashboard): add light/dark theme with sidebar toggle (#81)

compliance-dashboard/assets/main.css

@@ -61,6 +61,77 @@
     --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
 }
 
+/* ── Light theme tokens ──
+   Applied when the user has explicitly chosen light (`data-theme="light"`)
+   OR when their OS prefers light AND they have made no explicit choice. */
+:root[data-theme="light"] {
+    --bg-primary: #f5f7fb;
+    --bg-secondary: #ffffff;
+    --bg-card: rgba(255, 255, 255, 0.85);
+    --bg-card-solid: #ffffff;
+    --bg-card-hover: #f1f5fb;
+    --bg-elevated: #f8fafc;
+
+    --text-primary: #0c1426;
+    --text-secondary: #475569;
+    --text-tertiary: #8a9bb4;
+
+    --accent: #0070d4;
+    --accent-hover: #0080f0;
+    --accent-muted: rgba(0, 112, 212, 0.10);
+    --accent-glow: 0 0 20px rgba(0, 112, 212, 0.10);
+
+    --border: #e2e8f0;
+    --border-bright: #cbd5e1;
+    --border-accent: rgba(0, 112, 212, 0.30);
+
+    --danger: #dc2626;
+    --danger-bg: rgba(220, 38, 38, 0.08);
+    --warning: #d97706;
+    --warning-bg: rgba(217, 119, 6, 0.08);
+    --success: #16a34a;
+    --success-bg: rgba(22, 163, 74, 0.08);
+    --info: #2563eb;
+    --info-bg: rgba(37, 99, 235, 0.08);
+    --orange: #ea580c;
+    --orange-bg: rgba(234, 88, 12, 0.08);
+}
+
+@media (prefers-color-scheme: light) {
+    :root:not([data-theme="dark"]) {
+        --bg-primary: #f5f7fb;
+        --bg-secondary: #ffffff;
+        --bg-card: rgba(255, 255, 255, 0.85);
+        --bg-card-solid: #ffffff;
+        --bg-card-hover: #f1f5fb;
+        --bg-elevated: #f8fafc;
+
+        --text-primary: #0c1426;
+        --text-secondary: #475569;
+        --text-tertiary: #8a9bb4;
+
+        --accent: #0070d4;
+        --accent-hover: #0080f0;
+        --accent-muted: rgba(0, 112, 212, 0.10);
+        --accent-glow: 0 0 20px rgba(0, 112, 212, 0.10);
+
+        --border: #e2e8f0;
+        --border-bright: #cbd5e1;
+        --border-accent: rgba(0, 112, 212, 0.30);
+
+        --danger: #dc2626;
+        --danger-bg: rgba(220, 38, 38, 0.08);
+        --warning: #d97706;
+        --warning-bg: rgba(217, 119, 6, 0.08);
+        --success: #16a34a;
+        --success-bg: rgba(22, 163, 74, 0.08);
+        --info: #2563eb;
+        --info-bg: rgba(37, 99, 235, 0.08);
+        --orange: #ea580c;
+        --orange-bg: rgba(234, 88, 12, 0.08);
+    }
+}
+
 
 /* ── Reset & Base ── */
 
@@ -396,6 +467,44 @@ code {
     background: rgba(0, 200, 255, 0.06);
 }
 
+.theme-toggle {
+    background: none;
+    border: none;
+    border-top: 1px solid var(--border);
+    color: var(--text-secondary);
+    padding: 11px 18px;
+    cursor: pointer;
+    display: flex;
+    align-items: center;
+    gap: 11px;
+    font-family: var(--font-body);
+    font-size: 13.5px;
+    font-weight: 500;
+    transition: color 0.2s, background 0.2s;
+    width: 100%;
+    text-align: left;
+}
+
+.theme-toggle:hover {
+    color: var(--accent);
+    background: var(--accent-muted);
+}
+
+.theme-toggle svg {
+    flex-shrink: 0;
+    opacity: 0.75;
+    transition: opacity 0.2s;
+}
+
+.theme-toggle:hover svg {
+    opacity: 1;
+}
+
+.sidebar.collapsed .theme-toggle {
+    justify-content: center;
+    padding: 11px 0;
+}
+
 .sidebar.collapsed .sidebar-header {
     padding: 22px 0;
     justify-content: center;
@@ -3889,3 +3998,33 @@ tbody tr:last-child td {
 .copyable code, .copyable .mono { flex: 1; min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
 .code-snippet-wrapper { position: relative; }
 .code-snippet-header { display: flex; align-items: center; justify-content: space-between; margin-bottom: 4px; gap: 8px; }
+
+
+/* ═══════════════════════════════════════════════════════════════
+   LIGHT THEME — surface overrides for the few hardcoded dark
+   colors that don't go through CSS custom properties.
+   ═══════════════════════════════════════════════════════════════ */
+
+:root[data-theme="light"] .main-content {
+    background-image: radial-gradient(circle at 1px 1px, rgba(100, 116, 139, 0.18) 1px, transparent 0);
+}
+:root[data-theme="light"] .code-block {
+    background: #f8fafc;
+    color: #0c1426;
+}
+:root[data-theme="light"] .graph-stab-overlay {
+    background: radial-gradient(ellipse at center, rgba(245, 247, 251, 0.92) 0%, rgba(245, 247, 251, 0.98) 100%);
+}
+
+@media (prefers-color-scheme: light) {
+    :root:not([data-theme="dark"]) .main-content {
+        background-image: radial-gradient(circle at 1px 1px, rgba(100, 116, 139, 0.18) 1px, transparent 0);
+    }
+    :root:not([data-theme="dark"]) .code-block {
+        background: #f8fafc;
+        color: #0c1426;
+    }
+    :root:not([data-theme="dark"]) .graph-stab-overlay {
+        background: radial-gradient(ellipse at center, rgba(245, 247, 251, 0.92) 0%, rgba(245, 247, 251, 0.98) 100%);
+    }
+}