Add proboctl core skeleton and build system

Introduce the proboctl CLI entry point, root command, version,
completion, iostreams, shared cmdutil helpers (flags, table, JSON,
time formatting), API client with pagination, config management,
goreleaser configuration, and build system integration.

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

GNUmakefile

@@ -46,6 +46,9 @@ PROBOD_BIN_EXTRA_DEPS=
 PROBOD_BIN=	bin/probod
 PROBOD_SRC=	cmd/probod/main.go
 
+PROBOCTL_BIN=	bin/proboctl
+PROBOCTL_SRC=	cmd/proboctl/main.go
+
 ifndef SKIP_APPS
 PROBOD_BIN_EXTRA_DEPS += \
 	@probo/console \
@@ -119,7 +122,7 @@ coverage-combined: coverage-report test-e2e-coverage ## Generate combined covera
 	$(GO) tool cover -html=coverage-combined.out -o=coverage-combined.html
 
 .PHONY: build
-build: bin/probod
+build: bin/probod bin/proboctl
 
 .PHONY: sbom-docker
 sbom-docker: docker-build
@@ -176,6 +179,10 @@ bin/probod: pkg/server/api/connect/v1/schema/schema.go \
 	@probo/emails
 	$(GO_BUILD) -o $(PROBOD_BIN) $(PROBOD_SRC)
 
+.PHONY: bin/proboctl
+bin/proboctl:
+	$(GO_BUILD) -o $(PROBOCTL_BIN) $(PROBOCTL_SRC)
+
 .PHONY: @probo/emails
 @probo/emails:
 	$(NPM) --workspace $@ run build