feat: add conditions to deployment chain configuration

What would you like to be added:

a way to configure conditions on deployment chain triggers so that downstream apps only get deployed based on the outcome of the upstream deployment. right now a chain fires all matchers unconditionally regardless of whether the first deployment succeeded or failed.

there's actually already a commented-out stub for this in the codebase at pkg/configv1/application.go:

// TODO: Add conditions to deployment chain configuration.
// Conditions *DeploymentChainTriggerCondition `json:"conditions,omitempty"`

something like this would make sense:

pipeline:
  stages:
    - name: K8S_SYNC
  chain:
    conditions:
      status: SUCCESS
    applicationMatchers:
      - name: myapp-prod

Why is this needed:

without this, a failed staging deployment still triggers production. the whole point of chaining deployments is to gate on the previous result, and right now that gate doesn't exist. you'd have to manually cancel downstream deployments after a failure which defeats the purpose.

Start with the commented condition stub in pkg/configv1/application.go, then trace how deployment chain triggers and applicationMatchers are processed. Define the configuration and execution path for the shown status: SUCCESS condition, and verify that downstream applications run only when the upstream deployment has the matching outcome.