Add Valkey and PostgreSQL (closes #9)

Install valkey-server, valkey-tools and postgresql from apt. Ubuntu
26.04 ships Valkey 9 and PostgreSQL 18, replacing the postgresql16 the
audit pinned.

Model: deepseek-v4-pro

build.sh

@@ -31,7 +31,14 @@ apt-get -y install --no-install-recommends \
     zstd sqlite3 \
     libvips-dev libvips-tools libheif-dev libheif-plugin-aomenc \
     imagemagick ghostscript \
-    ruby ruby-dev bundler
+    ruby ruby-dev bundler \
+    valkey-server valkey-tools postgresql
+
+# Link the PostgreSQL server binaries onto PATH. They live under a versioned
+# directory (/usr/lib/postgresql/*/bin); the client psql is already on PATH.
+for p in postgres initdb pg_ctl; do
+    ln -s /usr/lib/postgresql/*/bin/"$p" /usr/local/bin/"$p"
+done
 
 # --- Go (latest) -------------------------------------------------------------
 gover="$(curl -fsSL 'https://go.dev/VERSION?m=text' | head -n1)"
@@ -102,6 +109,10 @@ rm -rf /usr/share/doc /usr/share/man /usr/share/info /usr/share/lintian
 find /usr/share/locale -mindepth 1 -maxdepth 1 ! -name 'en*' ! -name 'locale.alias' -exec rm -rf {} +
 rm -rf /root/.cache /root/.npm /root/.config /root/go /tmp/* /var/tmp/*
 
+# Valkey opens its log file at startup; recreate the log directory the
+# cleanup above removed, with its package owner.
+install -d -o valkey -g adm -m 2750 /var/log/valkey
+
 # --- sanity ------------------------------------------------------------------
 go version
 govulncheck -version
@@ -116,6 +127,13 @@ magick --version
 gs --version
 ruby --version
 bundle --version
+valkey-server --version
+valkey-cli --version
+valkey-server /etc/valkey/valkey.conf
+valkey-cli ping
+valkey-cli shutdown nosave
+psql --version
+postgres --version
 hugo version
 node --version
 npm --version