[ci skip] Move Terraform modules into stack directories

Move all 88 service modules (66 individual + 22 platform) from
modules/kubernetes/<service>/ into their corresponding stack directories:

- Service stacks: stacks/<service>/module/
- Platform stack: stacks/platform/modules/<service>/

This collocates module source code with its Terragrunt definition.
Only shared utility modules remain in modules/kubernetes/:
ingress_factory, setup_tls_secret, dockerhub_secret, oauth-proxy.

All cross-references to shared modules updated to use correct
relative paths. Verified with terragrunt run --all -- plan:
0 adds, 0 destroys across all 68 stacks.

stacks/f1-stream/module/files/internal/auth/context.go

@@ -0,0 +1,20 @@
+package auth
+
+import (
+	"context"
+
+	"f1-stream/internal/models"
+)
+
+type contextKey string
+
+const userKey contextKey = "user"
+
+func ContextWithUser(ctx context.Context, user *models.User) context.Context {
+	return context.WithValue(ctx, userKey, user)
+}
+
+func UserFromContext(ctx context.Context) *models.User {
+	user, _ := ctx.Value(userKey).(*models.User)
+	return user
+}