Remove Vue scaffolding and add design system foundation

Strip default Vue components (HelloWorld, TheWelcome, icons, AboutView),
base.css, and placeholder assets. Add Sora font (self-hosted WOFF2),
Electric Dusk color palette, and design system spec.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

spec/design-system.md

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+# Design System
+
+This document defines the visual design language for fete. All frontend implementation must follow these specifications.
+
+## Principles
+
+- **Mobile-first / App-native feel** — not a classic website. Think installed app, not browser page.
+- **Desktop:** centered narrow column (max ~480px), gradient background fills the rest.
+- **Generous whitespace** — elements breathe, nothing cramped.
+- **WCAG AA contrast** as baseline for all color choices.
+- **Accessibility is a baseline requirement** — not an afterthought (per project statutes).
+
+## Color Palette: Electric Dusk
+
+Chosen for best balance of style, broad appeal, and accessibility.
+
+| Role               | Hex       | Description        |
+|--------------------|-----------|--------------------|
+| Gradient Start     | `#F06292` | Pink               |
+| Gradient Mid       | `#AB47BC` | Purple             |
+| Gradient End       | `#5C6BC0` | Indigo blue        |
+| Accent (CTAs)      | `#FF7043` | Deep orange        |
+| Text (light mode)  | `#1C1C1E` | Near black         |
+| Text (dark mode)   | `#FFFFFF` | White              |
+| Surface (light)    | `#FFF5F8` | Pinkish white      |
+| Surface (dark)     | `#1B1730` | Deep indigo-black  |
+| Card (light)       | `#FFFFFF` | White              |
+| Card (dark)        | `#2A2545` | Muted indigo       |
+
+### Primary Gradient
+
+```css
+background: linear-gradient(135deg, #F06292 0%, #AB47BC 50%, #5C6BC0 100%);
+```
+
+### Usage Rules
+
+- Gradient for hero/splash areas and page backgrounds — not as direct text background for body copy.
+- Cards and content areas use solid surface colors with high-contrast text.
+- Accent color (`#FF7043`) for primary action buttons with dark text (`#1C1C1E`).
+- White text on gradient mid/end passes WCAG AA (4.82:1 and 4.86:1).
+- White text on gradient start passes AA-large (3.06:1) — use for headings 18px+ only.
+
+## Typography: Sora
+
+Contemporary geometric sans-serif with slightly rounded terminals. Modern and friendly without being childish.
+
+- **Font:** Sora
+- **License:** SIL Open Font License 1.1 (OFL)
+- **Source:** https://github.com/sora-xor/sora-font
+- **Format:** Self-hosted WOFF2. No external CDN. No Google Fonts.
+- **Weights:** 400 (Regular), 500 (Medium), 600 (SemiBold), 700 (Bold), 800 (ExtraBold)
+
+### Weight Usage
+
+| Context          | Weight | Size guideline  |
+|------------------|--------|-----------------|
+| Body text        | 400    | 0.85–1rem       |
+| Labels           | 600–700| 0.8–0.9rem      |
+| Headlines        | 700–800| 1.2–1.6rem      |
+| Buttons          | 700–800| 1rem            |
+| Small/meta text  | 400–500| 0.75–0.85rem    |
+
+## Component Patterns
+
+### Card-Style Form Fields
+
+- Rounded corners (`border-radius: 14px`)
+- Generous padding (`0.9rem 1rem`)
+- White/card-colored background on gradient pages
+- Subtle shadow (`box-shadow: 0 2px 8px rgba(0,0,0,0.1)`)
+- Bold label (font-weight 700), regular-weight input text
+
+### Buttons
+
+- Rounded corners matching card fields (`border-radius: 14px`)
+- Accent color background with dark text
+- Bold/ExtraBold weight (700–800)
+- Subtle shadow for depth
+
+### Layout
+
+- Mobile: full-width content with horizontal padding (~1.2rem)
+- Desktop: centered column, max-width ~480px, gradient background fills viewport
+- Vertical spacing between elements: ~0.75rem (compact), ~1.2rem (sections)