feat(ui): electric Bat-Computer redesign — cyan→magenta theme

Cinematic full-page backdrop: per-theme Bat-Computer board image,
scroll-panned (S→E→SE→NE) via CSS scroll-driven animation behind a
legibility scrim — replaces the grid/aura motif.

- Accent retuned royal-blue → the board's cyan→magenta; headline runs a
  cyan→magenta electric sweep; gradient primary CTA + scroll-progress line.
- Display face: self-hosted Chakra Petch (OFL) on hero + section titles.
- Skill chips reworked as circuit-node chips (glowing via + gradient hover
  outline); frosted-glass cards with a cyan→magenta hover hairline; section
  eyebrows get a gradient tick.
- Remove unused BackgroundGrid component + grid assets.

All CSS-only / zero external requests / no inline JS — strict CSP and A+
security headers preserved.

src/styles/tokens.css

@@ -17,22 +17,26 @@
   --text-dim: #9aa7b8;
   --text-faint: #61708a;
 
-  /* Accent — single restrained teal */
-  --accent: #5eead4;
-  --accent-strong: #2dd4bf;
-  --accent-ink: #042f2a; /* text on an accent fill */
-  --accent-dim: rgba(94, 234, 212, 0.12);
-  --accent-line: rgba(94, 234, 212, 0.28);
-  --accent-glow: rgba(45, 212, 191, 0.22);
+  /* Accent — electric cyan→magenta, merged with the Bat-Computer board */
+  --accent: #3fbaf5; /* cyan-blue (the board's left side) */
+  --accent-2: #e879f9; /* magenta (the board's right side) */
+  --accent-strong: #1f9fe0;
+  --accent-ink: #04161f; /* text on an accent fill */
+  --accent-dim: rgba(63, 186, 245, 0.12);
+  --accent-line: rgba(63, 186, 245, 0.3);
+  --accent-glow: rgba(63, 186, 245, 0.32);
 
   /* Grid / topology motif */
   --grid-line: rgba(148, 163, 184, 0.06);
 
-  /* Fonts — system stacks only (zero external requests). */
+  /* Fonts — system stacks (zero external requests) + one self-hosted display face. */
   --font-sans: "Inter var", ui-sans-serif, system-ui, -apple-system, "Segoe UI",
     Roboto, Helvetica, Arial, sans-serif;
   --font-mono: ui-monospace, "JetBrains Mono", "Cascadia Code", "SF Mono",
     Menlo, Consolas, "Liberation Mono", monospace;
+  /* Display face — Chakra Petch (self-hosted woff2, OFL). Used ONLY on the hero
+     name + section titles; body stays in --font-sans for readability. */
+  --font-display: "Chakra Petch", var(--font-sans);
 
   /* Fluid type scale */
   --step--1: clamp(0.8rem, 0.76rem + 0.2vw, 0.9rem);
@@ -77,12 +81,15 @@
   --text-dim: #475467;
   --text-faint: #6b7689;
 
-  --accent: #0d9488;
-  --accent-strong: #0f766e;
-  --accent-ink: #ecfdf5;
-  --accent-dim: rgba(13, 148, 136, 0.1);
-  --accent-line: rgba(13, 148, 136, 0.3);
-  --accent-glow: rgba(13, 148, 136, 0.16);
+  /* Accent — same electric cyan→magenta as dark, dropped in value for contrast
+     on the light sandstone board. */
+  --accent: #0c8fce; /* deeper cyan reads on white */
+  --accent-2: #c026d3; /* magenta partner */
+  --accent-strong: #0a72a6;
+  --accent-ink: #f2fbff;
+  --accent-dim: rgba(12, 143, 206, 0.1);
+  --accent-line: rgba(12, 143, 206, 0.32);
+  --accent-glow: rgba(192, 38, 211, 0.16);
 
   --grid-line: rgba(15, 23, 42, 0.05);