feat: enhance dashboard with PRs, adherence, activity, progression chart, and muscle heatmap

Add 3 new stat cards (Last Workout, Personal Records, Adherence Rate),
recent activity table, progression timeline chart, and muscle group
recency heatmap to the dashboard. Remove Total Volume card.

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

app/templates/pages/dashboard.html

@@ -4,6 +4,7 @@
 
 {% block head_extra %}
 <script src="https://cdn.jsdelivr.net/npm/chart.js@4"></script>
+<script src="https://cdn.jsdelivr.net/npm/chartjs-adapter-date-fns@3"></script>
 {% endblock %}
 
 {% block content %}
@@ -28,6 +29,15 @@
     {% include "partials/volume_chart.html" %}
 </article>
 
+<!-- Recent Activity -->
+{% include "partials/recent_activity.html" %}
+
+<!-- Progression Timeline -->
+{% include "partials/progression_chart.html" %}
+
+<!-- Muscle Group Heatmap -->
+{% include "partials/muscle_heatmap.html" %}
+
 <!-- Exercise Progress Links -->
 <article>
     <header><h3>Per-Exercise Progress</h3></header>
@@ -45,5 +55,9 @@
 
 <!-- Export -->
 {% include "partials/export_form.html" %}
+
 {% endif %}
+
+<!-- Import -->
+{% include "partials/import_form.html" %}
 {% endblock %}