Phase 0: project scaffold and build pipeline

Go module (codeberg.org/mix/selfpost), two command skeletons (panel,
selfpost-backup) sharing internal/buildinfo for the -ldflags version stamp,
Makefile (static CGO_ENABLED=0 build), AGPL-3.0 LICENSE, README skeleton and
.gitattributes forcing LF (container scripts must not get CRLF).

Verified on the dev server: go vet clean, make build produces statically
linked binaries, version stamping works.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Makefile

@@ -0,0 +1,31 @@
+# SelfPost build.
+#
+# The version is stamped into both binaries and MUST match the Docker image tag
+# (spec 7.5.A: backup/restore compatibility check). Override on the command line:
+#
+#     make build VERSION=1.3.0
+#
+# CGO is disabled to keep the binaries fully static (modernc.org/sqlite is pure
+# Go, so no cgo is required) — see spec 7.1.
+
+VERSION ?= dev
+MODULE  := codeberg.org/mix/selfpost
+LDFLAGS := -X $(MODULE)/internal/buildinfo.Version=$(VERSION)
+GOFLAGS := -trimpath
+
+.PHONY: all build vet test clean
+
+all: vet build
+
+build:
+	CGO_ENABLED=0 go build $(GOFLAGS) -ldflags "$(LDFLAGS)" -o bin/panel ./cmd/panel
+	CGO_ENABLED=0 go build $(GOFLAGS) -ldflags "$(LDFLAGS)" -o bin/selfpost-backup ./cmd/selfpost-backup
+
+vet:
+	go vet ./...
+
+test:
+	go test ./...
+
+clean:
+	rm -rf bin