Replace mock dashboard data with real database queries and report-derived timelines

- Replace mock statistics in stats_summarizer.py with real SQLAlchemy queries
  against DMARCReport, ReportRecord, and Domain models
- Replace random compliance timeline in domains.py with real data from ReportStore
- Remove unused `import random` from domains.py
- Add comprehensive tests for StatsSummarizer (global/domain/caching)
- Add tests for compliance timeline (deterministic, multi-report aggregation)
- Mark Dashboard Visualizations as complete in TODO.md

Agent-Logs-Url: https://github.com/christianlouis/dmarq/sessions/ea784ce3-2c1c-45f8-ad6d-46e92cf15ed7

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

backend/app/tests/test_dashboard_timeline.py

@@ -0,0 +1,147 @@
+"""Tests for the domain compliance timeline with real data."""
+
+from fastapi.testclient import TestClient
+
+from app.services.report_store import ReportStore
+
+
+def _add_report_to_store(
+    domain, report_id, begin_ts, end_ts, total, passed, failed, org_name="test.org"
+):
+    """Helper to add a report to the ReportStore with integer timestamps."""
+    store = ReportStore.get_instance()
+    store.add_report(
+        {
+            "domain": domain,
+            "report_id": report_id,
+            "org_name": org_name,
+            "begin_date": begin_ts,
+            "end_date": end_ts,
+            "begin_timestamp": begin_ts,
+            "end_timestamp": end_ts,
+            "policy": "none",
+            "records": [],
+            "summary": {
+                "total_count": total,
+                "passed_count": passed,
+                "failed_count": failed,
+            },
+        }
+    )
+
+
+class TestComplianceTimeline:
+    """Tests that the compliance timeline returns real data instead of mock."""
+
+    def test_timeline_has_entries_after_upload(self, client: TestClient):
+        """When a domain has reports, the timeline should have entries."""
+        _add_report_to_store("example.com", "rpt-001", 1597449600, 1597535999, 10, 8, 2)
+
+        response = client.get("/api/v1/domains/example.com/reports?limit=10")
+        assert response.status_code == 200
+        data = response.json()
+        timeline = data["compliance_timeline"]
+        assert len(timeline) >= 1
+
+    def test_timeline_uses_real_dates(self, client: TestClient):
+        """Timeline dates should come from actual report begin_dates."""
+        _add_report_to_store("example.com", "rpt-001", 1597449600, 1597535999, 10, 8, 2)
+
+        response = client.get("/api/v1/domains/example.com/reports?limit=10")
+        data = response.json()
+        timeline = data["compliance_timeline"]
+
+        # The begin_date=1597449600 is 2020-08-15
+        dates = [point["date"] for point in timeline]
+        assert "2020-08-15" in dates
+
+    def test_timeline_compliance_rate_is_deterministic(self, client: TestClient):
+        """Compliance rate should be deterministic, not random."""
+        _add_report_to_store("example.com", "rpt-001", 1597449600, 1597535999, 10, 8, 2)
+
+        resp1 = client.get("/api/v1/domains/example.com/reports?limit=10")
+        resp2 = client.get("/api/v1/domains/example.com/reports?limit=10")
+
+        timeline1 = resp1.json()["compliance_timeline"]
+        timeline2 = resp2.json()["compliance_timeline"]
+        assert timeline1 == timeline2
+
+    def test_timeline_empty_for_domain_with_no_valid_dates(self, client: TestClient):
+        """A domain with begin_date=0 should have an empty timeline."""
+        store = ReportStore.get_instance()
+        store.add_report(
+            {
+                "domain": "empty-timeline.com",
+                "report_id": "rpt-empty",
+                "org_name": "test",
+                "begin_date": 0,
+                "end_date": 0,
+                "policy": "none",
+                "records": [],
+                "summary": {"total_count": 0, "passed_count": 0, "failed_count": 0},
+            }
+        )
+
+        response = client.get("/api/v1/domains/empty-timeline.com/reports?limit=10")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["compliance_timeline"] == []
+
+    def test_timeline_handles_iso_string_dates(self, client: TestClient):
+        """Timeline should handle reports with ISO-format string dates."""
+        from app.api.api_v1.endpoints.domains import _build_compliance_timeline
+
+        store = ReportStore.get_instance()
+        store.add_report(
+            {
+                "domain": "isodate.com",
+                "report_id": "rpt-iso",
+                "org_name": "test",
+                "begin_date": "2020-08-15T00:00:00",
+                "end_date": "2020-08-15T23:59:59",
+                "policy": "none",
+                "records": [],
+                "summary": {"total_count": 10, "passed_count": 9, "failed_count": 1},
+            }
+        )
+
+        timeline = _build_compliance_timeline(store, "isodate.com")
+        assert len(timeline) == 1
+        assert timeline[0].date == "2020-08-15"
+        assert timeline[0].compliance_rate == 90.0
+
+
+class TestBuildComplianceTimelineMultipleReports:
+    """Test timeline aggregation with multiple reports."""
+
+    def test_multiple_reports_same_day(self, client: TestClient):
+        """Multiple reports on the same day should be aggregated."""
+        _add_report_to_store("multi.com", "rpt-1", 1597449600, 1597535999, 10, 8, 2)
+        _add_report_to_store("multi.com", "rpt-2", 1597449600, 1597535999, 10, 6, 4)
+
+        response = client.get("/api/v1/domains/multi.com/reports?limit=10")
+        assert response.status_code == 200
+        data = response.json()
+        timeline = data["compliance_timeline"]
+
+        assert len(timeline) == 1
+        assert timeline[0]["date"] == "2020-08-15"
+        # Aggregated: 14 passed out of 20 total = 70%
+        assert timeline[0]["compliance_rate"] == 70.0
+
+    def test_reports_on_different_days(self, client: TestClient):
+        """Reports on different days should produce separate timeline points."""
+        _add_report_to_store("days.com", "rpt-d1", 1597449600, 1597535999, 10, 10, 0)
+        _add_report_to_store("days.com", "rpt-d2", 1597536000, 1597622399, 10, 5, 5)
+
+        response = client.get("/api/v1/domains/days.com/reports?limit=10")
+        assert response.status_code == 200
+        data = response.json()
+        timeline = data["compliance_timeline"]
+
+        assert len(timeline) == 2
+        # Sorted by date
+        assert timeline[0]["date"] == "2020-08-15"
+        assert timeline[0]["compliance_rate"] == 100.0
+        assert timeline[1]["date"] == "2020-08-16"
+        assert timeline[1]["compliance_rate"] == 50.0