Fix detailed Timeline statistics regression

[stef-k]

Closes #557

Summary

• allow valid partial country/region hierarchy in PostgreSQL detailed-statistics projections
• explicitly map grouped counts to the existing integer DTO contract
• use Wayfarer's custom alert on both Timeline views without exposing response or exception details

Validation

• focused Timeline/service/controller tests: 53 passed
• PostgreSQL detailed-statistics tests: 2 passed
• focused client regression: 1 passed
• build: succeeded with 0 warnings/errors
• LOC checker: passed with no changed-file baseline growth
• Code Guard: approved one-time exception for the two pre-existing oversized Timeline scripts; each shrinks by one line and adds no responsibility

Browser evidence

Authenticated browser smoke was unavailable because the local protected provider credential cannot be decrypted by the isolated test host and the documented live login did not authenticate. The failure is reproduced and fixed at the real PostgreSQL service seam; custom-alert placement is covered at the client source seam. No bespoke harness was added.

No database migration is required.