feat: add Forest, Mono, and Cyberpunk color themes

Forest — deep green surfaces (#0a130d base) with green-400 accent.
  Inspired by terminal emulators and dark mode IDE forest schemes.

Mono — near-black zinc-950 surface with pure white/zinc-100 accent.
  Minimal high-contrast monochromatic palette for distraction-free reading.

Cyber — near-black blue surface with neon cyan-400 accent and dracula-palette
  success/danger colors. Cyberpunk aesthetic with neon glow feel.

Changes:
- app.css: three new [data-theme] blocks with full token sets
- +layout.svelte: added forest/mono/cyber to THEMES array (before light themes)
- profile/+page.svelte: same additions with i18n label functions
- messages/*.json: translated names in all 5 locales (en/fr/ru/pt/id)

ui/src/app.css

@@ -97,6 +97,48 @@
 	--color-success:   #16a34a;   /* green-600 */
 }
 
+/* ── Forest theme — dark green ────────────────────────────────────────── */
+[data-theme="forest"] {
+	--color-brand:     #4ade80;   /* green-400 */
+	--color-brand-dim: #16a34a;   /* green-600 */
+	--color-surface:   #0a130d;   /* custom near-black green */
+	--color-surface-2: #111c14;   /* custom dark green */
+	--color-surface-3: #1a2e1e;   /* custom mid green */
+	--color-muted:     #6b9a77;   /* custom muted green */
+	--color-text:      #e8f5e9;   /* custom light green-tinted white */
+	--color-border:    #1e3a24;   /* custom green border */
+	--color-danger:    #f87171;   /* red-400 */
+	--color-success:   #4ade80;   /* green-400 */
+}
+
+/* ── Mono theme — pure dark with white accent ─────────────────────────── */
+[data-theme="mono"] {
+	--color-brand:     #f4f4f5;   /* zinc-100 — white accent */
+	--color-brand-dim: #a1a1aa;   /* zinc-400 */
+	--color-surface:   #09090b;   /* zinc-950 */
+	--color-surface-2: #18181b;   /* zinc-900 */
+	--color-surface-3: #27272a;   /* zinc-800 */
+	--color-muted:     #71717a;   /* zinc-500 */
+	--color-text:      #f4f4f5;   /* zinc-100 */
+	--color-border:    #27272a;   /* zinc-800 */
+	--color-danger:    #f87171;   /* red-400 */
+	--color-success:   #4ade80;   /* green-400 */
+}
+
+/* ── Cyberpunk theme — dark with neon cyan/magenta accents ────────────── */
+[data-theme="cyber"] {
+	--color-brand:     #22d3ee;   /* cyan-400 — neon cyan */
+	--color-brand-dim: #06b6d4;   /* cyan-500 */
+	--color-surface:   #050712;   /* custom near-black blue */
+	--color-surface-2: #0d1117;   /* custom dark blue-black */
+	--color-surface-3: #161b27;   /* custom dark blue */
+	--color-muted:     #6272a4;   /* dracula comment blue */
+	--color-text:      #e2e8f0;   /* slate-200 */
+	--color-border:    #1e2d45;   /* custom dark border */
+	--color-danger:    #ff5555;   /* dracula red */
+	--color-success:   #50fa7b;   /* dracula green */
+}
+
 html {
 	background-color: var(--color-surface);
 	color: var(--color-text);