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/models.py

@@ -4,6 +4,21 @@ from core.models import TimeStampedModel, UUIDPrimaryKeyModel
 from leads.models import Lead
 
 
+class PageView(UUIDPrimaryKeyModel, TimeStampedModel):
+    """One successful GET of a public marketing page."""
+
+    path = models.CharField(max_length=512, db_index=True)
+
+    class Meta:
+        ordering = ["-created_at"]
+        indexes = [
+            models.Index(fields=["created_at", "path"]),
+        ]
+
+    def __str__(self) -> str:
+        return self.path or "/"
+
+
 class UTMVisit(UUIDPrimaryKeyModel, TimeStampedModel):
     correlation_id = models.CharField(max_length=64, db_index=True)
     path = models.CharField(max_length=512, blank=True)