Bug: Object count + insights show same number across all tiers

[rubenvdlinde]

Observation

On the application detail page for Permit Flow (uuid `09f72a5f-b0f9-45e5-8120-b1030694ab50`), all three KPI cards on the version-pill row show identical numbers regardless of which version is selected:

Version (pill)	URL	Active users	Object count	Files	Audit events
Production	(no `?_version=`)	0	246	0	0
Development	`?_version=development`	0	246	0	0
Staging (not retested but expected same)	…	…	…	…	…

The newly seeded development register `openbuilt-permit-flow-development` should be empty, so `object count: 246` is wrong.

Suspected root cause

`ApplicationInsightsController` / its underlying service probably ignores the `versionUuid` URL path segment and aggregates the whole `openbuilt` register (or the whole organisation) instead of the per-version register `openbuilt-permit-flow-{tier}`.

Need to:

1. Trace `GET /api/applications/{appUuid}/versions/{versionUuid}/insights`
2. Verify the underlying counter queries scope by the version's `register` field, not the global `openbuilt` register.
3. Add a unit test that distinguishes per-tier counts.

Repro

1. Wizard-create app with 3 tiers (development, staging, production).
2. Open detail page.
3. Switch between pills.
4. KPIs should reflect each tier's register; instead all read 246.

Surfaced while verifying #74 (dev → staging → prod workflow).

[rubenvdlinde]

Fixed in #78 (merged). substituteVersionContext now namespaces config.schema alongside config.register so insights aggregate against the correct per-version schema-set. Validated by 3 new PHPUnit cases (happy path, idempotency, empty-prefix backward-compat).