feat(web): introduce FabledSword design system tokens + Tailwind aliases

Add the canonical FS token palette (surfaces, text, action, semantic,
accent, radii, fonts) as CSS custom properties under web/src/lib/styles/
fabledsword-tokens.css, with a [data-fs-app="minstrel"] hook reserved
for future per-app accent overrides. Wire the tokens through Tailwind by
aliasing semantic colour utilities (bg-background, bg-surface,
bg-surface-hover, text-text-primary/secondary/muted, border-border,
bg-action-primary/secondary/destructive, accent, warning/error/info) to
the new variables, plus rounded-sm..xl and font-display/sans/mono. Load
Fraunces, Inter, and JetBrains Mono (400/500 only) via Google Fonts and
default the body to Inter. Existing components inherit the new palette
without per-page changes.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/tailwind.config.js

@@ -4,15 +4,39 @@ export default {
   theme: {
     extend: {
       colors: {
+        background: 'var(--fs-obsidian)',
         surface: {
-          900: '#14161a',
-          800: '#1a1d22',
-          700: '#2a2f36'
+          DEFAULT: 'var(--fs-iron)',
+          hover: 'var(--fs-slate)'
+        },
+        border: {
+          DEFAULT: 'var(--fs-pewter)'
         },
         text: {
-          primary: '#e8ecf2',
-          secondary: '#cdd3db'
-        }
+          primary: 'var(--fs-parchment)',
+          secondary: 'var(--fs-vellum)',
+          muted: 'var(--fs-ash)'
+        },
+        action: {
+          primary: 'var(--fs-moss)',
+          secondary: 'var(--fs-bronze)',
+          destructive: 'var(--fs-oxblood)'
+        },
+        accent: 'var(--fs-accent)',
+        warning: 'var(--fs-warning)',
+        error: 'var(--fs-error)',
+        info: 'var(--fs-info)'
+      },
+      borderRadius: {
+        sm: 'var(--fs-radius-sm)',
+        md: 'var(--fs-radius-md)',
+        lg: 'var(--fs-radius-lg)',
+        xl: 'var(--fs-radius-xl)'
+      },
+      fontFamily: {
+        display: ['Fraunces', 'Georgia', 'serif'],
+        sans: ['Inter', 'system-ui', 'sans-serif'],
+        mono: ['JetBrains Mono', 'ui-monospace', 'monospace']
       }
     }
   },