feat: deep black dark + pure white light theme tokens

- Canvas: oklch(1 0 0) light / oklch(0 0 0) dark (true black)
- Surface: oklch(0.98 0 0) light / oklch(0.07 0 0) dark
- Ink: oklch(0.08 0 0) light / oklch(1 0 0) dark (pure white)
- Ink-soft: oklch(0.40 0 0) light / oklch(0.72 0 0) dark
- Border: oklch(0.92 0 0) light / oklch(0.17 0 0) dark
- Accent: oklch(0.45 0.18 250) light / oklch(0.68 0.20 250) dark
- Shadow-card updated for both modes

app/globals.css

@@ -6,12 +6,12 @@
 /* === Design Tokens === */
 @theme {
   /* Colors — Light mode defaults */
-  --color-canvas: oklch(0.99 0 0);
-  --color-surface: oklch(0.97 0.005 240);
-  --color-ink: oklch(0.15 0.006 240);
-  --color-ink-soft: oklch(0.45 0.008 240);
-  --color-border: oklch(0.88 0.008 240);
-  --color-accent: oklch(0.55 0.18 250);
+  --color-canvas: oklch(1 0 0);
+  --color-surface: oklch(0.98 0 0);
+  --color-ink: oklch(0.08 0 0);
+  --color-ink-soft: oklch(0.40 0 0);
+  --color-border: oklch(0.92 0 0);
+  --color-accent: oklch(0.45 0.18 250);
 
   /* Fonts — override defaults */
   --font-sans: "Inter", ui-sans-serif, system-ui, sans-serif;
@@ -30,7 +30,7 @@
   --text-5xl: 3rem; --text-5xl--line-height: 1.1;
 
   /* Shadows */
-  --shadow-card: 0 1px 3px rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
+  --shadow-card: 0 1px 3px oklch(0 0 0 / 0.08);
 
   /* Animations */
   --animate-fade-in: fade-in 0.3s ease-out;
@@ -83,11 +83,13 @@
 
 /* === Dark mode token overrides === */
 .dark {
-  --color-canvas: oklch(0.12 0.02 240);
-  --color-surface: oklch(0.18 0.02 240);
-  --color-ink: oklch(0.96 0.005 240);
-  --color-ink-soft: oklch(0.75 0.01 240);
-  --color-border: oklch(0.28 0.025 240);
+  --color-canvas: oklch(0 0 0);
+  --color-surface: oklch(0.07 0 0);
+  --color-ink: oklch(1 0 0);
+  --color-ink-soft: oklch(0.72 0 0);
+  --color-border: oklch(0.17 0 0);
+  --color-accent: oklch(0.68 0.20 250);
+  --shadow-card: 0 1px 4px oklch(1 0 0 / 0.06);
 }
 
 /* === Blog typography === */