feat: Dan Mode (third theme), Pico CSS notes, cycle theme toggle

Dan Mode: pure white backgrounds, electric blue text (#0000ff), nuclear
yellow accents (#ffff00), hot magenta borders (#ff00ff), red labels,
glowing box-shadows. Maximum saturation. Hostile to human vision by design.

Theme toggle now cycles light → dark → dan → light (icons: 🌙 😎 ☀️).

PICO_CSS.md: documents [role=button] color clobber, palette scoping rules,
and theme toggling pattern for future reference.

src/app.css

@@ -54,6 +54,107 @@
 }
 [data-theme=dark] { --color-label: #a0a09a; }
 
+/* ── DAN MODE ──────────────────────────────────────────────────────────────── */
+/* Screaming bright colors. Offensive to the eyes by design.                   */
+[data-theme=dan] {
+  color-scheme: light;
+
+  /* Base */
+  --pico-background-color: #ffffff;
+  --pico-color: #0000ff;             /* pure electric blue body text */
+  --pico-muted-color: #ff6600;       /* screaming orange for muted text */
+  --pico-muted-border-color: #ff00ff;
+
+  /* Cards */
+  --pico-card-background-color: #ffffff;
+  --pico-card-border-color: #ff00ff; /* magenta borders */
+  --pico-card-box-shadow: 0 0 12px 2px #ffff00, 0 0 4px 1px #ff00ff;
+
+  /* Primary — nuclear yellow */
+  --pico-primary: #cccc00;
+  --pico-primary-background: #ffff00;
+  --pico-primary-border: #cccc00;
+  --pico-primary-hover: #aaaa00;
+  --pico-primary-hover-background: #eeee00;
+  --pico-primary-hover-border: #aaaa00;
+  --pico-primary-focus: rgba(255, 255, 0, 0.6);
+  --pico-primary-inverse: #000000;   /* black text on yellow buttons */
+
+  /* Secondary — hot magenta */
+  --pico-secondary: #ff00ff;
+  --pico-secondary-background: #dd00dd;
+  --pico-secondary-border: #ff00ff;
+  --pico-secondary-hover: #ff44ff;
+  --pico-secondary-hover-background: #ff00ff;
+  --pico-secondary-inverse: #ffffff;
+
+  /* Contrast */
+  --pico-contrast: #000000;
+  --pico-contrast-background: #000000;
+  --pico-contrast-inverse: #ffff00;
+
+  /* Form elements */
+  --pico-form-element-background-color: #ffffcc;
+  --pico-form-element-border-color: #ff00ff;
+  --pico-form-element-color: #0000ff;
+  --pico-form-element-active-border-color: #ff0000;
+  --pico-form-element-focus-color: rgba(255, 0, 255, 0.5);
+
+  /* App-specific */
+  --color-label: #ff0000;            /* red labels */
+}
+
+/* Dan Mode: result tile text — override the [role=button] white-text reset */
+[data-theme=dan] .result-tile {
+  --pico-color: initial;
+  color: #0000ff;
+  background-color: #ffffff;
+  border-color: #ff00ff;
+  box-shadow: 0 0 8px 1px #ffff00;
+}
+
+[data-theme=dan] .result-tile:hover,
+[data-theme=dan] .result-tile.highlighted {
+  background-color: #ffff00;
+  border-color: #ff0000;
+  color: #000000;
+  box-shadow: 0 0 16px 4px #ff00ff;
+}
+
+[data-theme=dan] .result-label {
+  color: #ff0000;
+}
+
+/* Dan Mode: highlight bar */
+[data-theme=dan] .highlighted-result {
+  background-color: #ffff00;
+  border-color: #ff0000 !important;
+  box-shadow: 0 0 20px 4px #ff00ff;
+}
+
+[data-theme=dan] .highlighted-eq-from,
+[data-theme=dan] .highlighted-eq-to {
+  color: #000000;
+}
+
+[data-theme=dan] .highlighted-eq-sep {
+  color: #ff0000;
+}
+
+/* Dan Mode: nav / header */
+[data-theme=dan] header {
+  background-color: #ffff00;
+  border-bottom: 3px solid #ff00ff;
+}
+
+[data-theme=dan] header strong {
+  color: #ff0000;
+}
+
+[data-theme=dan] header nav a {
+  color: #0000ff !important;
+}
+
 /* ── Results grid ──────────────────────────────────────────────────────────── */
 .results-grid {
   display: grid;