design: WorkoutPage Hevy-style redesign + AlternativeModal + backend API

- Add GET /api/exercises/:id/alternatives endpoint
- Add GET /api/exercises/:id/last-workout endpoint
- New AlternativeModal component for swapping exercises
- WorkoutPage: single-tap logging, +/- buttons, rest timer
- Updated Icons with new workout icons
- Polish: card shadows, borders, micro-interactions
- Tasks directory for project management

.planning/phases/03-design-polish/03-01-PLAN.md

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+# Plan 03-01: Login/Onboarding Polish
+
+**\Goal:** Transform auth pages from "hobby app" to enterprise-grade fitness product
+
+## Current Issues
+
+1. **Emoji branding** - $ \nCravl\" looks amateur, violates design system (no emojis)
+2. **Basic form styling** - No visual polish, lacks professional feel
+3. **Missing brand presence** - No logo mark, weak visual identity
+4. **Form interactions** - No focus states, weak error presentation
+
+## Implementation
+
+### Files to Modify
+
+- frontend/src/pages/LoginPage.jsx
+- frontend/src/pages/RegisterPage.jsx
+- frontend/src/App.css (auth section)
+
+### Changes
+
+**1. Branding Component**
+Create SVG logo mark - abstract barbell/rack silhouette (single color, clean lines):
+const Logo = () => (
+  <svg viewBox="0 0 48 48" className="logo-mark">
+    <path d="M12 16h4v16h-4zM20 12h8v24h-8zM32 16h4v16h-4z" fill="currentColor"/>
+    <rect x="8" y="20" width="4" height="8"/>
+    <rect x="36" y="20" width="4" height="8"/>
+  </svg>
+);
+
+**2. LoginPage Changes**
+- Remove  \nGavl\" h1
+- Add Logo component above \"Logga in\"
+- Update to: <Logo /> + <h1 className="auth-title">Logga in</h1>
+- Add subtle tagline under title: \"Din personliga träningspartner\"
+- Improve error display with animation/fade-in
+
+**3. RegisterPage Changes**
+- Same logo/title treatment
+- Tagline: \"Börja din träningsresa\"
+- Form field focus improvements
+
+**4. CSS Updates (App.css auth section)**
+Add professional polish: gradient background, improved card styling with shadows, focus states, animations, proper spacing.
+
+- auth-page: add gradient bg, better spacing
+- auth-card: add borter, shadow, padding
+- logo-mark: 56px svg, accent color
+- auth-title: centered, font-2xl
+- auth-tagline: text-secondary, small
+- input focus: indicator (accent border + glow)
+- button: hover/active states, scale effect
+- error: animated error box
+
+
+## Verification
+
+- [ ] No emojis remain on auth pages
+- [ ] Logo mark displays correctly (56px, accent color)
+- [ ] Tagline visible under title
+- [ ] Focus states work on inputs (accent border + glow)
+- [ ] Error messages animate in smoothly
+- [ ] Button hover/active states feel responsive
+- [ ] Card has proper shadow and border
+- [ ] Form is centered vertically on mobile/desktop
+
+## Blockers
+
+None - frontend only changes.