FINERACT-2715: Mark Activation Date as required in Client Entity import template

[Samer-Melhem-FOO]

Description

The Client Entity bulk import template did not visually indicate that "Activation Date" is a required column. ClientEntityImportHandler requires a valid Activation Date whenever the "Active" column is set to true, so imports failed on rows left blank without any indication from the template that the field was mandatory.

This changes the column header in ClientEntityWorkbookPopulator from "Activation Date " to "Activation Date* ", consistent with how other conditionally-required columns (e.g. "Active*") are marked on the same sheet.

JIRA

https://issues.apache.org/jira/browse/FINERACT-2715

Test plan

• ./gradlew :fineract-provider:compileJava passes
• Verified no existing test asserts the previous header string (integration test ClientEntityWorkbookPopulatorTest does not hardcode it)

[Samer-Melhem-FOO]

The only failing check here is run-e2e-tests / E2E Tests (Shard 4 of 20). Looking at the log, it fails at the jibDockerBuild step before any tests run, with:

I/O error for image [registry-1.docker.io/azul/zulu-openjdk-alpine]:
java.net.SocketException
Network is unreachable

This looks like a transient Docker Hub registry connectivity issue on the runner, unrelated to this PR's change (a single header-label fix in ClientEntityWorkbookPopulator). All other 19/20 E2E shards, all 15/15 DB-matrix shards (MariaDB/MySQL/PostgreSQL), and every other check (checkstyle, spotless, spotbugs, etc.) passed.

Could a maintainer re-run the failed job? I don't have the permissions to trigger a re-run myself. Thanks!