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.

Dockerfile

@@ -0,0 +1,57 @@
+# Lint stage
+# golangci/golangci-lint:v2.12.2-alpine
+FROM golangci/golangci-lint:v2.12.2-alpine@sha256:91b27804074a0bacea298707f016911e60cf0cdbc6c7bf5ccacb5f0606d18d60 AS lint
+
+RUN apk add --no-cache make build-base
+
+WORKDIR /src
+
+# Copy go mod files first for better layer caching
+COPY go.mod go.sum ./
+RUN go mod download
+
+# Copy source code
+COPY . .
+
+# Run formatting check and linter
+RUN make fmt-check
+RUN make lint
+
+# Build stage
+# golang:1.26.4-alpine
+FROM golang:1.26.4-alpine@sha256:3ad57304ad93bbec8548a0437ad9e06a455660655d9af011d58b993f6f615648 AS builder
+
+# Depend on lint stage passing
+COPY --from=lint /src/go.sum /dev/null
+
+ARG VERSION=dev
+
+# Install build deps plus the sqlite3 and zstd CLIs the tests/tool shell out to
+RUN apk add --no-cache make build-base sqlite zstd
+
+WORKDIR /src
+
+# Copy go mod files first for better layer caching
+COPY go.mod go.sum ./
+RUN go mod download
+
+# Copy source code
+COPY . .
+
+# Run tests
+RUN make test
+
+# Build (pure Go, no CGO required since we use modernc.org/sqlite)
+RUN CGO_ENABLED=0 go build -o /bsdaily ./cmd/bsdaily
+
+# Runtime stage
+# alpine:3.21
+FROM alpine:3.21@sha256:48b0309ca019d89d40f670aa1bc06e426dc0931948452e8491e3d65087abc07d
+
+# bsdaily shells out to sqlite3, zstdmt, zstdcat at runtime
+RUN apk add --no-cache ca-certificates sqlite zstd
+
+# Copy binary from builder
+COPY --from=builder /bsdaily /usr/local/bin/bsdaily
+
+ENTRYPOINT ["/usr/local/bin/bsdaily"]