Add end-to-end tests for TLS RPT report ingestion and WebSocket event handling

- Implemented tests for ingesting TLS RPT reports from emails and ensuring they are stored correctly in the database.
- Added tests to verify that the same report can be ingested multiple times without duplication.
- Created tests for backfilling reports that were previously delivered to the inbox.
- Developed WebSocket event handling tests to ensure events are correctly routed to subscribers based on mailbox ownership.
- Included tests for the mail API to validate session handling, mailbox isolation, and error mapping.
- Ensured that the API rejects unauthorized requests and handles malformed JSON gracefully.

migrations/0009_report_ingestion_idempotency.down.sql

@@ -0,0 +1,2 @@
+DROP INDEX IF EXISTS uq_tls_rpt_reports_org_report;
+DROP INDEX IF EXISTS uq_dmarc_reports_org_report;