Add public PageView tracking for portal analytics (#4)

## Summary
Closes #3.

- Add `PageView` model + migration for successful public marketing GET hits
- Wire `PublicPageViewMiddleware` (skips portal/admin/accounts/api/static/health/etc.; fails soft on DB errors)
- Portal analytics report: last-30-day views + top pages table
- Admin registration and tests

## Test plan
- [ ] Apply migration `analytics.0002_pageview`
- [ ] Hit `/` and `/about/` → rows in `PageView` / admin
- [ ] Hit `/healthz/`, `/portal/`, `/admin/` → no new pageviews
- [ ] Open portal Analytics → views count + Top pages look right
- [ ] `uv run python site/manage.py test analytics.tests`

Reviewed-on: #4

site/analytics/templates/analytics/report.html

@@ -2,11 +2,37 @@
 {% block title %}Analytics · Portal{% endblock %}
 {% block topbar_title %}Analytics{% endblock %}
 {% block portal_content %}
-<div class="stat-row">
+<div class="analytics-overview">
   <div class="stat-card">
     <div class="label">Views (last 30 days)</div>
-    <div class="value">{{ visits_last_30_days }}</div>
+    <div class="value">{{ pageviews_last_30_days }}</div>
   </div>
+  <div class="panel">
+    <div class="panel-h"><h2>Top pages</h2><span class="muted" style="font-size:12px">Public visits, last 30 days</span></div>
+    <div class="panel-b" style="padding:0">
+      <table class="table">
+        <thead>
+          <tr>
+            <th>Page</th>
+            <th>Visits</th>
+          </tr>
+        </thead>
+        <tbody>
+          {% for row in top_pages %}
+          <tr>
+            <td>{{ row.path }}</td>
+            <td>{{ row.count }}</td>
+          </tr>
+          {% empty %}
+          <tr><td colspan="2" class="empty-state">No public page views in the last 30 days.</td></tr>
+          {% endfor %}
+        </tbody>
+      </table>
+    </div>
+  </div>
+</div>
+
+<div class="stat-row">
   <div class="stat-card">
     <div class="label">UTM landings</div>
     <div class="value">{{ total_visits }}</div>