feat: restyle admin UI and add per-user sync run history

Adds a self-hosted stylesheet (no CDN dependencies) with a card-based
dashboard and color-coded status badges, and shows the last 10 sync
runs per user on the detail page.

app/web/templates/fragments/mfa_form.html

@@ -1,5 +1,6 @@
-<form method="post" action="/users/{{ user.id }}/garmin-mfa">
+<form method="post" action="/users/{{ user.id }}/garmin-mfa" class="stacked-form">
     <input type="hidden" name="csrf_token" value="{{ csrf_token }}">
-    <label>Garmin MFA code: <input type="text" name="code" maxlength="20" required></label>
+    <label for="mfa_code">Garmin MFA code</label>
+    <input type="text" id="mfa_code" name="code" maxlength="20" required>
     <button type="submit">Submit code</button>
 </form>

app/web/templates/fragments/sync_result.html

@@ -1,17 +1,45 @@
-<ul>
-    {% for outcome in outcomes %}
-    <li>
-        User {{ outcome.user_id if outcome.user_id is not none else "unknown" }}:
-        status={{ outcome.status }}
-        discovered={{ outcome.discovered }}
-        imported={{ outcome.imported }}
-        skipped={{ outcome.skipped }}
-        failed={{ outcome.failed }}
-        {% if outcome.message %}
-        &mdash; {{ outcome.message }}
-        {% endif %}
-    </li>
-    {% else %}
-    <li>No outcomes.</li>
-    {% endfor %}
-</ul>
+{% extends "base.html" %}
+
+{% block title %}Sync result - MyWhoosh Garmin Sync{% endblock %}
+
+{% block content %}
+<h1>Sync result</h1>
+<div class="page-actions">
+    <a class="btn secondary" href="/">Back to dashboard</a>
+</div>
+<div class="card">
+    <table>
+        <thead>
+            <tr>
+                <th>User</th>
+                <th>Status</th>
+                <th>Discovered</th>
+                <th>Imported</th>
+                <th>Skipped</th>
+                <th>Failed</th>
+            </tr>
+        </thead>
+        <tbody>
+            {% for outcome in outcomes %}
+            <tr>
+                <td>{{ outcome.user_id if outcome.user_id is not none else "unknown" }}</td>
+                <td><span class="badge badge-{{ outcome.status }}">{{ outcome.status }}</span></td>
+                <td>{{ outcome.discovered }}</td>
+                <td>{{ outcome.imported }}</td>
+                <td>{{ outcome.skipped }}</td>
+                <td>{{ outcome.failed }}</td>
+            </tr>
+            {% if outcome.message %}
+            <tr>
+                <td colspan="6" class="summary-error">{{ outcome.message }}</td>
+            </tr>
+            {% endif %}
+            {% else %}
+            <tr>
+                <td colspan="6" class="empty-state">No outcomes.</td>
+            </tr>
+            {% endfor %}
+        </tbody>
+    </table>
+</div>
+{% endblock %}