fix(Helpers): flagsmith.annotations emits duplicate keys when a custom annotation overrides a common one

[germangarces]

The flagsmith.annotations helper combines common.annotations with a resource's own annotations by printing both blocks one after the other. When the same key exists in both, the rendered output contains that key twice:

annotations:
    company.io/owner: platform         # from common.annotations
    company.io/owner: migrations-team   # from the resource

Duplicate keys are invalid YAML. Kubernetes and lenient parsers keep the last one, so applies usually work — but strict tools (kubeconform --strict, kubectl --strict, ArgoCD) reject it, and the manifest is misleading to read.

This affects every resource using the helper with the customAnnotations / commonValues form — services, ingresses, gateways.

Suggested fix

Merge the two maps into one before rendering (resource-specific key wins), instead of concatenating. A fresh-dict merge avoids mutating values:

merge (dict) $resourceAnnotations $commonAnnotations

How to reproduce

Set the same annotation key in both common.annotations and a resource's annotations, run helm template, observe the duplicate key.

Discovered while reviewing #542.