add 404/403 pages

static/css/style.css

@@ -5604,6 +5604,91 @@ select.control { cursor: pointer; }
   }
 }
 
+/* ================================================================
+   ERROR PAGES (404, 403)
+   ================================================================ */
+.page--error {
+  padding: 0;
+  max-width: none;
+}
+
+.error-pg {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  min-height: calc(100vh - 62px);
+  position: relative;
+  overflow: hidden;
+  background:
+    radial-gradient(ellipse 90% 70% at 50% 60%, #1c0e3e 0%, #100820 55%, var(--bg) 100%),
+    radial-gradient(ellipse 50% 40% at 80% 20%, rgba(155,140,240,.07) 0%, transparent 55%);
+}
+
+/* large suit watermark */
+.error-pg__suit {
+  position: absolute;
+  font-size: clamp(320px, 46vw, 660px);
+  color: rgba(155,140,240,.065);
+  line-height: 1;
+  pointer-events: none;
+  user-select: none;
+  top: 50%;
+  left: 50%;
+  transform: translate(-50%, -50%);
+  transition: none;
+}
+.error-pg--403 .error-pg__suit {
+  color: rgba(155,140,240,.06);
+}
+
+.error-pg__body {
+  position: relative;
+  z-index: 1;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  text-align: center;
+  gap: 0;
+  padding: clamp(32px, 5vw, 64px) clamp(24px, 5vw, 48px);
+}
+
+.error-pg__code {
+  font-family: var(--font-mono);
+  font-size: clamp(80px, 13vw, 148px);
+  font-weight: 900;
+  letter-spacing: -.04em;
+  line-height: 1;
+  background: linear-gradient(135deg, var(--accent) 0%, rgba(155,140,240,.35) 100%);
+  -webkit-background-clip: text;
+  -webkit-text-fill-color: transparent;
+  background-clip: text;
+  margin-bottom: 8px;
+}
+
+.error-pg__title {
+  font-size: clamp(28px, 4vw, 52px);
+  font-weight: 800;
+  color: var(--text);
+  letter-spacing: -.04em;
+  margin: 0 0 16px;
+  line-height: 1.1;
+}
+
+.error-pg__sub {
+  font-size: clamp(14px, 1.3vw, 16px);
+  color: rgba(255,255,255,.42);
+  max-width: 40ch;
+  line-height: 1.68;
+  margin: 0 0 28px;
+}
+
+.error-pg__actions {
+  display: flex;
+  gap: 12px;
+  flex-wrap: wrap;
+  justify-content: center;
+}
+
 /* ================================================================
    LANDING — hero kicker (replaces pill eyebrow in hero only)
    ================================================================ */