Add zstd and the sqlite3 CLI (closes #5)

Install zstd and sqlite3 from apt and check both in the smoke test.

Model: deepseek-v4-pro

README.md

@@ -35,6 +35,8 @@ Image: `git.eeqj.de/sneak/baseimage`, built for `linux/amd64` and
 | Python (latest) | `pyenv install`                | `/usr/local/pyenv/versions/*`  |
 | virtualenv      | apt, and pip in pyenv Python   | `virtualenv` on `PATH`         |
 | tzdata          | apt                            | `/usr/share/zoneinfo`          |
+| zstd            | apt                            | `/usr/bin/zstd`                |
+| sqlite3 (CLI)   | apt                            | `/usr/bin/sqlite3`             |
 
 Plus the usual odds and ends: `git`, `curl`, `wget`, `jq`, `rsync`,
 `openssh-client`, `zip`/`unzip`, `xz-utils`, `bzip2`, and the `-dev`

bin/test

@@ -24,6 +24,8 @@ docker run --rm "$img" bash -ec '
     shellcheck --version
     govulncheck -version
     TZ=America/New_York date +%Z
+    zstd --version
+    sqlite3 --version
 '
 
 echo "== $img: runit service lifecycle"

build.sh

@@ -27,7 +27,8 @@ apt-get -y install --no-install-recommends \
     libreadline-dev libsqlite3-dev libssl-dev libxml2-dev libxmlsec1-dev \
     tk-dev uuid-dev zlib1g-dev \
     shellcheck \
-    tzdata
+    tzdata \
+    zstd sqlite3
 
 # --- Go (latest) -------------------------------------------------------------
 gover="$(curl -fsSL 'https://go.dev/VERSION?m=text' | head -n1)"
@@ -106,6 +107,8 @@ govulncheck -version
 golangci-lint version
 shellcheck --version
 TZ=America/New_York date +%Z
+zstd --version
+sqlite3 --version
 hugo version
 node --version
 npm --version