feat(theme): R10 S1 — semantic status colors (danger/warn/success)

Add theme-scoped --danger/--warn/--success (+ -fg) tokens wired into the v4
@theme inline, replacing ~110 raw red/amber/emerald/green palette refs across
34 files. Fixes light-theme contrast failures (fixed Tailwind shades fell to
~1.7-3:1 on white). Status colors are scheme-independent — recognised by hue,
shifting only by theme to hold contrast (bright on dark bg, darkened on light).
Solid fills use the paired -fg text; @source inline guarantees the full -fg set
exists. IMDb rating gold kept as a deliberate decorative non-status exception.

frontend/src/index.css

@@ -1,5 +1,11 @@
 @import "tailwindcss";
 
+/* Guarantee the full status fill-text set exists even before first use, so any
+   bg-{status} fill always has a readable text-{status}-fg partner available
+   (Tailwind v4 only emits a utility when it sees it used; success-fg has no fill
+   consumer today). Keeps the semantic token set complete + future-proof. */
+@source inline("text-danger-fg text-warn-fg text-success-fg");
+
 /* `inline` is load-bearing: the color vars (--bg/--accent/… below) are redefined at
    runtime per html[data-scheme]/[data-theme], so utilities must inline the value and
    resolve it at the USE site, not reference a once-computed --color-* token. This also
@@ -14,6 +20,12 @@
   --color-muted: var(--muted);
   --color-accent: var(--accent);
   --color-accent-fg: var(--accent-fg);
+  --color-danger: var(--danger);
+  --color-danger-fg: var(--danger-fg);
+  --color-warn: var(--warn);
+  --color-warn-fg: var(--warn-fg);
+  --color-success: var(--success);
+  --color-success-fg: var(--success-fg);
 
   --font-sans: Inter, system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
 
@@ -657,6 +669,30 @@ html[data-scheme="matrix"][data-theme="light"] {
   --accent-fg: #ffffff;
 }
 
+/* ===== Semantic status colors (danger / warn / success) =====
+   Scheme-INDEPENDENT, theme-scoped: a status color is recognised by its conventional
+   hue (red=danger), so it stays constant across schemes and only shifts by theme to
+   hold contrast — bright on the near-black dark bg, darkened for ≥4.5:1 on the white
+   light bg. The scheme blocks above deliberately do NOT set these (lower specificity
+   here is fine — no scheme overrides them). Per-scheme override only if a real clash
+   surfaces. `-fg` is readable text ON a solid status fill. */
+html[data-theme="dark"] {
+  --danger: #f87171;
+  --danger-fg: #2a0a0a;
+  --warn: #fbbf24;
+  --warn-fg: #1f1400;
+  --success: #34d399;
+  --success-fg: #052016;
+}
+html[data-theme="light"] {
+  --danger: #dc2626;
+  --danger-fg: #ffffff;
+  --warn: #b45309;
+  --warn-fg: #ffffff;
+  --success: #047857;
+  --success-fg: #ffffff;
+}
+
 /* Toast auto-dismiss countdown bar (shrinks left-to-right to zero) */
 @keyframes toastbar {
   from {