feat: mobile-first redesign and layout improvements

## Major Changes

### Mobile-First Responsive Design
- Converted entire app to mobile-first single-column layout
- Constrained max-width to 448px (mobile phone width)
- Black margins on desktop, centered content
- Removed all multi-column grids (md:grid-cols-3)

### Header Reorganization (3-Row Layout)
- Row 1: App logo + title + version
- Row 2: Security badges + action buttons (Empty, Reset)
- Row 3: Navigation tabs (Create, Backup, Restore, Blender)
- Replaced text buttons with emoji icons (📋 clipboard, 🙈 privacy mask)
- Consistent button sizing across all tabs

### Font Size Reductions
- Reduced all button text sizes for mobile density
- Main buttons: py-4 → py-3, added text-sm
- Labels: text-xs → text-[10px]
- Placeholders: consistent text-[10px] across all inputs
- Input fields: text-sm → text-xs, p-4 → p-3

### Create Tab Improvements
- Changed "GENERATE NEW SEED" from button-style to banner
- Left-aligned banner with gradient background
- Equal-width button grid (12/24 Words, Backup/Seed Blender)
- Used grid-cols-2 for consistent sizing

### Backup Tab Improvements
- Simplified drag-drop area with 📎 emoji
- Reduced padding and text sizes
- Cleaner, shorter copy
- PGP label font size: text-xs → text-[12px]

### SeedBlender Component
- Reorganized mnemonic input cards: textarea on row 1, buttons on row 2
- QR button (left) and X button (right) alignment
- Consistent placeholder text sizing (text-[10px])
- Shortened dice roll placeholder text

### HTTPS Development Server
- Added @vitejs/plugin-basic-ssl for HTTPS in dev mode
- Configured server to listen on 0.0.0.0:5173
- Fixed Web Crypto API issues on mobile (requires secure context)
- Enables testing on iPhone via local network

## Technical Details
- All changes maintain cyberpunk theme and color scheme
- Improved mobile usability and visual consistency
- No functionality changes, pure UI/UX improvements

bun.lock

@@ -27,6 +27,7 @@
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         "@types/react": "^18.3.12",
         "@types/react-dom": "^18.3.1",
+        "@vitejs/plugin-basic-ssl": "^1.1.0",
         "@vitejs/plugin-react": "^4.3.4",
         "autoprefixer": "^10.4.20",
         "postcss": "^8.4.49",
@@ -263,6 +264,8 @@
 
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+
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