Add Helm tests for default image tag, improve values.yaml docs

Add tests verifying deployment and migrations-job use main-latest
as the default image tag. Add comment noting main-latest is mutable
and production deployments should pin to a specific version tag.

deploy/charts/litellm-helm/tests/deployment_tests.yaml

@@ -3,6 +3,12 @@ templates:
   - deployment.yaml
   - configmap-litellm.yaml
 tests:
+  - it: should use main-latest tag by default
+    template: deployment.yaml
+    asserts:
+      - equal:
+          path: spec.template.spec.containers[0].image
+          value: ghcr.io/berriai/litellm-database:main-latest
   - it: should work
     template: deployment.yaml
     set:

deploy/charts/litellm-helm/tests/migrations-job_tests.yaml

@@ -2,6 +2,15 @@ suite: test migrations job
 templates:
   - migrations-job.yaml
 tests:
+  - it: should use main-latest image tag by default
+    template: migrations-job.yaml
+    set:
+      migrationJob:
+        enabled: true
+    asserts:
+      - equal:
+          path: spec.template.spec.containers[0].image
+          value: ghcr.io/berriai/litellm-database:main-latest
   - it: should work with envVars
     template: migrations-job.yaml
     set:

deploy/charts/litellm-helm/values.yaml

@@ -9,7 +9,9 @@ image:
   # Use "ghcr.io/berriai/litellm-database" for optimized image with database
   repository: ghcr.io/berriai/litellm-database
   pullPolicy: Always
-  # Overrides the image tag whose default is "main-latest".
+  # Overrides the image tag. Defaults to "main-latest" (the latest main-branch build).
+  # For production use, override this with a specific version tag (e.g. "v1.x.y") to
+  # ensure reproducible deployments, since "main-latest" is a mutable tag.
   tag: "main-latest"
 
 imagePullSecrets: []