Add README, LICENSE, Makefile, Dockerfile, and CI

Add a detailed README, WTFPL LICENSE, and build/CI tooling modeled on
the vaultik repo (Makefile, multi-stage digest-pinned Dockerfile,
.gitea/workflows/check.yml). Bump Go to 1.26.4 and pin golangci-lint
to v2.12.2. gofmt existing sources so the new fmt-check gate passes.

Makefile

@@ -0,0 +1,71 @@
+.PHONY: all check test lint fmt fmt-check build clean deps test-coverage test-integration install release release-snapshot docker hooks
+
+# Version number
+VERSION := 0.1.0-dev
+
+# Default target
+all: bsdaily
+
+# Combined pre-commit/CI gate: lint, format check, then tests.
+check: lint fmt-check test
+
+# Run tests only.
+test:
+	go test -race -timeout 30s ./...
+
+# Check if code is formatted (read-only).
+fmt-check:
+	@test -z "$$(gofmt -l .)" || (echo "Files not formatted:" && gofmt -l . && exit 1)
+
+# Format code.
+fmt:
+	go fmt ./...
+
+# Run linter only.
+lint:
+	golangci-lint run ./...
+
+# Build binary (pure Go; no CGO required since we use modernc.org/sqlite).
+bsdaily: internal/*/*.go cmd/bsdaily/*.go
+	CGO_ENABLED=0 go build -o $@ ./cmd/bsdaily
+
+# Clean build artifacts.
+clean:
+	rm -f bsdaily
+	go clean
+
+# Install dependencies.
+deps:
+	go mod download
+	go install github.com/golangci/golangci-lint/cmd/golangci-lint@latest
+
+# Run tests with coverage.
+test-coverage:
+	go test -v -coverprofile=coverage.out ./...
+	go tool cover -html=coverage.out -o coverage.html
+
+# Run integration tests.
+test-integration:
+	go test -v -tags=integration ./...
+
+install: bsdaily
+	cp ./bsdaily $(HOME)/bin/
+
+# Build and publish release artifacts via goreleaser.
+release:
+	goreleaser release --clean
+
+# Dry-run a release build without publishing or tagging.
+release-snapshot:
+	goreleaser release --clean --snapshot
+
+# Build Docker image.
+docker:
+	docker build -t bsdaily .
+
+# Install pre-commit hook.
+hooks:
+	@printf '#!/bin/sh\nset -e\n' > .git/hooks/pre-commit
+	@printf 'go mod tidy\ngo fmt ./...\ngit diff --exit-code -- go.mod go.sum || { echo "go mod tidy changed files; please stage and retry"; exit 1; }\n' >> .git/hooks/pre-commit
+	@printf 'make check\n' >> .git/hooks/pre-commit
+	@chmod +x .git/hooks/pre-commit