feat: add dashboard change summaries

docs/development/roadmap.md

@@ -36,19 +36,17 @@ Recently improved:
 Implementation note:
 - The legacy `ReportStore` remains as a projection layer for existing report/dashboard code, but durable report data now lives in the database.
 
-## Active Milestone: Meaningful Reports
+## Completed Milestone: Meaningful Reports
 
 Objective: turn parsed DMARC data into administrator-friendly reports.
 
-Priority tasks:
-- Add "what changed" summaries for newly observed senders and sudden compliance drops.
-
 Delivered:
 - Dashboard time-series charts show daily mail volume, compliance rate, and failure rate.
 - Top sending sources show DMARC, SPF, and DKIM pass/fail breakdowns on the dashboard.
 - Per-domain timelines include daily volume, pass, fail, compliance-rate, and failure-rate rollups.
 - Domain reports can be exported to CSV for a selected date range.
 - Source reports include actionable recommendations for unknown sources, SPF-only passes, DKIM-only passes, full failures, and unenforced policies.
+- What changed summaries identify newly observed senders and sudden compliance drops.
 
 Quality bar:
 - A domain owner can understand who sends mail as their domain, which sources fail, and what to fix next.

docs/milestones.md

@@ -71,9 +71,9 @@ Delivered:
 Exit criteria:
 - A user can connect a mailbox, run a backfill, see exactly what was imported or skipped, and trust that totals are not double-counted.
 
-## Milestone 5: Dashboard and Meaningful Reports - In Progress
+## Milestone 5: Dashboard and Meaningful Reports - Complete
 
-Status: In progress
+Status: Complete
 
 Goal: convert raw DMARC data into useful operational reporting.
 
@@ -83,6 +83,7 @@ Delivered:
 - Per-domain report timeline and daily rollups.
 - Exportable reports for a selected domain and date range.
 - Clear recommendations for common cases: unknown source, SPF-only pass, DKIM-only pass, full fail, and policy not enforced.
+- What changed summaries for newly observed sources and sudden compliance drops.
 
 Exit criteria:
 - A domain owner can answer: who is sending as my domain, what is failing, what changed recently, and what should I fix next?

docs/todo.md

@@ -150,7 +150,7 @@ This file tracks the specific implementation tasks for each milestone of the DMA
 ### Meaningful Reports
 - [x] Add per-domain daily rollups
 - [x] Add sender/source pass/fail totals
-- [ ] Add newly observed source detection
+- [x] Add newly observed source detection
 - [x] Add exportable domain reports
 - [x] Add actionable recommendations for common DMARC failure patterns