feat(actions): row-level Run/Test handlers for Sources/Jobs/Synchronizations

[rubenvdlinde]

Summary

Stacked on #828. Restores the ability to trigger backend Run/Test actions from the UI — post chain-C the per-schema action modals were orphaned and unreachable, leaving no way to run a job or test a source from the index pages.

The legacy modals (RunJob 175 LoC, TestJob 176 LoC, TestSource 193 LoC, RunSynchronization 345 LoC, TestSynchronization 222 LoC) had rich in-modal progress/result panels. Re-creating those bespoke modals stays scoped as a future follow-up (see src/modals/README.md).

This PR ships the lean version: manifest-declared row actions that resolve to small POST handlers showing a success/error toast. Users check the corresponding *Logs page (one Actions-menu click away after #828) for run details.

Wiring

• New src/handlers/actionHandlers.js — 5 handler functions, ~10 LoC each, built via a shared makePostHandler factory:
  • testSourceHandler → POST /api/sources/test/{id}
  • runJobHandler → POST /api/jobs/run/{id}
  • testJobHandler → POST /api/jobs/test/{id}
  • runSynchronizationHandler → POST /api/synchronizations/{id}/run
  • testSynchronizationHandler → POST /api/synchronizations/{id}/test
• src/registry.js — exports the handlers alongside the existing ImportIndex. CnIndexPage's resolveHandler looks up function entries in this registry by name.
• src/manifest.json — three index pages gain new row actions before their existing View logs entry:
  • Sources: + Test connection
  • Jobs: + Run now, + Test (dry run)
  • Synchronizations: + Run now, + Test (dry run)

Backend endpoints are all post-chain-C live entries from appinfo/routes.php, untouched.

Out of scope

• Test mapping row action — needs an in-dialog input picker (legacy TestMapping.vue was 142 LoC + 3 sub-components). Bespoke modal follow-up.
• Add rule to endpoint row action — needs a rule selector dialog (legacy AddEndpointRule.vue was 172 LoC). Bespoke modal follow-up.
• Rich in-modal result panel — would re-introduce the chain-A modal pattern. Toast + log-page navigation is the leaner replacement.

Test plan

• After chore(manifest): trim log menu + curate row actions + columns + form fields #828 + chain-E merge, this PR auto-retargets to development
• On Sources index, click row Actions → Test connection → toast appears, source log gains a new entry
• On Jobs index, click row Actions → Run now → toast appears, job log gains a new entry
• On Synchronizations index, click row Actions → Test (dry run) → toast appears
• CI: build, lint, phpcs/phpmd/psalm/phpstan