fix: drop pause annotation from primary ScaledObject

[bryantvolk]

tldr

vibe slop, sorry. this issue is my bane

Fixes #1934

Why

When Flagger creates the primary KEDA ScaledObject, it copies annotations from the source so scaledobject.keda.sh/transfer-hpa-ownership can take over an existing HPA. If the source is already paused, that copy also includes autoscaling.keda.sh/paused-replicas: "0". Resume only clears the source, so KEDA never builds the primary HPA and the primary Deployment stays at 0 replicas while the Canary reports Succeeded.

This strips the pause annotation on primary create and leaves source pause and resume unchanged.

Scope

• makeObjectMetaSo in pkg/canary/scaled_object_reconciler.go deletes keda.PausedReplicasAnnotation after filterMetadata.
• Test_reconcilePrimaryScaledObject pauses the source before create and asserts the primary does not carry the pause key and still has transfer-hpa-ownership.

Out of scope: healing an already-stuck primary without recreate. Update still only rewrites metadata when the spec diffs and init is false.

Tradeoffs

• Rejected applying includeLabelsByPrefix on create. Default --include-label-prefix is empty, so that filter would drop transfer-hpa-ownership and regress KEDA Scaled Object Primary creation failed due to workload already managed by the hpa #1646.
• Rejected stopping annotation copy. That copy is what PR 1677 added for HPA to ScaledObject migration.

Blast Radius

Canaries that use autoscalerRef.kind: ScaledObject get an unpaused primary on create and recreate. Source ScaledObjects still pause at 0 after bootstrap. After upgrade, delete each stuck -primary ScaledObject once so Flagger recreates it without the pause annotation.

Verification

Failing before the fix:

--- FAIL: Test_reconcilePrimaryScaledObject (0.00s)
    scaled_object_reconciler_test.go:35:
        	Error: map[string]string{"autoscaling.keda.sh/paused-replicas":"0", "scaledobject.keda.sh/transfer-hpa-ownership":"true"} should not contain "autoscaling.keda.sh/paused-replicas"

Passing after:

go test ./pkg/canary -run 'Test_reconcilePrimaryScaledObject|Test_pauseScaledObject|Test_resumeScaledObject' -count=1
ok  	github.com/fluxcd/flagger/pkg/canary	0.990s

go test ./... passed. make test failed in hack/verify-codegen.sh because kube_codegen.sh is missing from the local k8s.io/code-generator module. That script is unchanged by this PR.