feat(webhook): trigger brain-sync on Gitea push instead of 15-min poll

Adds POST /webhooks/brain-sync: verifies Gitea's HMAC-SHA256 signature,
checks the push is to mathias/brain main, then creates a one-off Job from
the existing brain-sync CronJob's template (same script the 15-min poll
already runs, just triggered on-demand). Off by default -- opt in via
GITEA_WEBHOOK_SECRET, since it needs Job-create RBAC in the "brain"
namespace a fresh deploy won't have.

10 new tests (internal/webhook), including a fake-clientset reactor to
simulate server-side GenerateName expansion, which the plain fake tracker
doesn't do on its own.

Needs (follow-up, infra repo): RBAC granting ingestion's ServiceAccount
get on cronjobs/brain-sync + create on jobs in the brain namespace, the
GITEA_WEBHOOK_SECRET env, and the actual Gitea webhook registration.

ingestion/go.mod

@@ -2,17 +2,57 @@ module github.com/mathiasbq/hyperguild/ingestion
 
 go 1.26.1
 
-require github.com/stretchr/testify v1.11.1
+require (
+	github.com/stretchr/testify v1.11.1
+	k8s.io/api v0.31.3
+	k8s.io/apimachinery v0.31.3
+	k8s.io/client-go v0.31.3
+)
 
 require (
-	github.com/kr/text v0.2.0 // indirect
+	github.com/emicklei/go-restful/v3 v3.11.0 // indirect
+	github.com/fxamacker/cbor/v2 v2.7.0 // indirect
+	github.com/go-logr/logr v1.4.2 // indirect
+	github.com/go-openapi/jsonpointer v0.19.6 // indirect
+	github.com/go-openapi/jsonreference v0.20.2 // indirect
+	github.com/go-openapi/swag v0.22.4 // indirect
+	github.com/gogo/protobuf v1.3.2 // indirect
+	github.com/golang/protobuf v1.5.4 // indirect
+	github.com/google/gnostic-models v0.6.8 // indirect
+	github.com/google/go-cmp v0.6.0 // indirect
+	github.com/google/gofuzz v1.2.0 // indirect
+	github.com/google/uuid v1.6.0 // indirect
+	github.com/imdario/mergo v0.3.6 // indirect
+	github.com/josharian/intern v1.0.0 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/lestrrat-go/jwx/v2 v2.1.6 // indirect
+	github.com/mailru/easyjson v0.7.7 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
 	github.com/rogpeppe/go-internal v1.15.0 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
+	github.com/x448/float16 v0.8.4 // indirect
+	golang.org/x/net v0.26.0 // indirect
+	golang.org/x/oauth2 v0.21.0 // indirect
+	golang.org/x/term v0.28.0 // indirect
+	golang.org/x/time v0.3.0 // indirect
+	google.golang.org/protobuf v1.34.2 // indirect
+	gopkg.in/evanphx/json-patch.v4 v4.12.0 // indirect
+	gopkg.in/inf.v0 v0.9.1 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
+	k8s.io/klog/v2 v2.130.1 // indirect
+	k8s.io/kube-openapi v0.0.0-20240228011516-70dd3763d340 // indirect
+	k8s.io/utils v0.0.0-20240711033017-18e509b52bc8 // indirect
+	sigs.k8s.io/json v0.0.0-20221116044647-bc3834ca7abd // indirect
+	sigs.k8s.io/structured-merge-diff/v4 v4.4.1 // indirect
+	sigs.k8s.io/yaml v1.4.0 // indirect
 )
 
 require (
 	git.d-ma.be/mathias/mcp-chassis v0.2.0
-	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
 	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.4.0 // indirect
 	github.com/goccy/go-json v0.10.3 // indirect
 	github.com/jackc/pgpassfile v1.0.0 // indirect
@@ -24,7 +64,7 @@ require (
 	github.com/lestrrat-go/httprc v1.0.6 // indirect
 	github.com/lestrrat-go/iter v1.0.2 // indirect
 	github.com/lestrrat-go/option v1.0.1 // indirect
-	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
 	github.com/segmentio/asm v1.2.0 // indirect
 	golang.org/x/crypto v0.32.0 // indirect
 	golang.org/x/sync v0.17.0 // indirect