refactor(ai-core): typesafe handlers decoupled from service impl

[Schmarvinius]

1. Remove AICoreServiceImpl field from AbstractCrudHandler / all handlers. Obtain the service reference from EventContext at invocation time instead.
2. Replace string-literal event names ("resourceGroupForTenant", "stop", etc.) with compile-safe constants either generated via CDS build (cds4j generated event context interfaces) or declared as String constants on the interface/entity.
3. Switch to typesafe handler APIs: define typed EventContext subinterfaces for each action (e.g., ResourceGroupForTenantContext, StopDeploymentContext) so handlers declare typed parameters instead of doing Map extraction from context.get("data").
4. Verify that DeploymentHandler, ResourceGroupHandler, ConfigurationHandler, MockEntityHandler, and AICoreApplicationServiceHandler are also decoupled.

[github-actions]

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