fix(theme): R10 S1 follow-ups — dedicated info token + restore collapsed hovers

- Add --info/--info-fg (blue; dark #60a5fa / light #2563eb) so info notifications
  stop borrowing --accent, which collided with a status colour in schemes whose
  accent shares its hue (YouTube red = error, Slate orange = warn, Matrix/Forest
  green = success). Toaster info tone accent -> info.
- Restore hover feedback the codemod flattened: 'bg-X ... hover:bg-X' /
  'text-X ... hover:text-X' collapsed to a no-op once both shades mapped to one
  shadeless token. Reuse the house hover:opacity-{80,90} idiom (ConfirmProvider
  danger button, DownloadCenter error link).

frontend/src/index.css

@@ -4,7 +4,7 @@
    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");
+@source inline("text-danger-fg text-warn-fg text-success-fg text-info-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
@@ -20,6 +20,8 @@
   --color-muted: var(--muted);
   --color-accent: var(--accent);
   --color-accent-fg: var(--accent-fg);
+  --color-info: var(--info);
+  --color-info-fg: var(--info-fg);
   --color-danger: var(--danger);
   --color-danger-fg: var(--danger-fg);
   --color-warn: var(--warn);
@@ -683,6 +685,8 @@ html[data-theme="dark"] {
   --warn-fg: #1f1400;
   --success: #34d399;
   --success-fg: #052016;
+  --info: #60a5fa;
+  --info-fg: #08172e;
 }
 html[data-theme="light"] {
   --danger: #dc2626;
@@ -691,6 +695,8 @@ html[data-theme="light"] {
   --warn-fg: #ffffff;
   --success: #047857;
   --success-fg: #ffffff;
+  --info: #2563eb;
+  --info-fg: #ffffff;
 }
 
 /* Toast auto-dismiss countdown bar (shrinks left-to-right to zero) */