feat(dashboard): polish header logo, stat cards, calendar and animations

- Replace gravl icon text with Logo component in dashboard header
- Stat cards: gradient depth + per-card colour accent (orange/green/amber)
- Calendar today: pulsing glow animation; workout days get subtle brand tint
- Arrow nudge animation on today-workout-card hover
- Section stagger fade-in on page load (calendar → coach → stats)
- Larger stat-value font (3xl) with tighter letter-spacing
- Consistent gap spacing in dashboard-main (space-6)

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

frontend/src/pages/Dashboard.jsx

@@ -1,6 +1,7 @@
 import { useState, useEffect } from 'react'
 import { useAuth } from '../context/AuthContext'
 import { Icon, getActivityIconName } from '../components/Icons'
+import Logo from '../components/Logo'
 
 const API_URL = '/api'
 
@@ -90,7 +91,10 @@ function Dashboard({ onStartWorkout, onNavigate }) {
     <div className="dashboard">
       <header className="dashboard-header">
         <div className="header-top">
-          <h1 className="brand-title"><Icon name="gravl" size={22} /> Gravl</h1>
+          <h1 className="brand-title">
+            <Logo />
+            <span className="brand-name">Gravl</span>
+          </h1>
           <nav className="nav-menu">
             <button className="nav-btn active"><Icon name="home" size={18} /></button>
             <button className="nav-btn" onClick={() => onNavigate('progress')}><Icon name="chart" size={18} /></button>