Light mode: ticket-ID hover preview follows the theme (#23)

.ticket-preview-popup used var(--lt-surface), which is not defined anywhere, so
the background always fell through to the hardcoded #0a0e14. In light mode that
left a near-black panel — and since the rule set no `color`, the inherited
near-black body text was effectively invisible on it. The border was hardcoded
neon green and the shadow a heavy rgba(0,0,0,0.5).

Now uses --bg-card / --text-primary / --accent-green-border / --shadow-color,
and .preview-id uses --accent-cyan instead of the undefined --lt-cyan.

base.css gains the two tokens the light theme was missing (--accent-green-border
and --shadow-color), synced from web_template 0d633bd.

Verified with computed styles in headless chromium: light body-text contrast on
the panel goes from invisible to 17.7:1, dark stays at 13.2:1, and the ID accent
clears 3:1 in both themes.

assets/css/base.css

@@ -66,6 +66,7 @@
   --accent-green-bright: #33FFAA;
   --accent-green-dim:    rgba(0,255,136,0.10);
   --accent-green-border: rgba(0,255,136,0.22);
+  --shadow-color:        rgba(0,0,0,0.5);
 
   /* --- Error / Critical --- */
   --accent-red:     #FF2D55;
@@ -3640,6 +3641,8 @@ html[data-theme="light"] {
   --accent-red-dim:      rgba(181,0,31,0.10);
   --accent-amber-dim:    rgba(138,90,0,0.10);
   --accent-cyan-border:  rgba(0,98,184,0.28);
+  --accent-green-border: rgba(0,109,53,0.28);
+  --shadow-color:        rgba(50,80,130,0.18);
 
   /* — Glows become subtle drop shadows in light mode — */
   --glow-orange:         0 0 0 1px rgba(196,78,0,0.25),  0 1px 6px rgba(196,78,0,0.18);