feat: restructure PostgreSQL setup with base variant

postgres-base/.env.example

@@ -0,0 +1,4 @@
+POSTGRES_USER=postgres
+POSTGRES_PASSWORD=postgres
+POSTGRES_DB=postgres
+POSTGRES_PORT=5432

postgres-base/000_extensions.sql

@@ -0,0 +1,3 @@
+CREATE EXTENSION IF NOT EXISTS citext;
+CREATE EXTENSION IF NOT EXISTS pg_trgm;
+CREATE EXTENSION IF NOT EXISTS pgcrypto;

postgres-base/Dockerfile

@@ -0,0 +1,6 @@
+FROM postgres:18-alpine
+
+COPY 000_extensions.sql /docker-entrypoint-initdb.d/
+
+HEALTHCHECK --interval=10s --timeout=5s --retries=5 \
+  CMD pg_isready -U ${POSTGRES_USER} -d ${POSTGRES_DB}

postgres-base/compose.yml

@@ -0,0 +1,16 @@
+services:
+  postgres:
+    # run `just build postgres` first
+    image: db-postgres:latest
+    restart: unless-stopped
+    environment:
+      POSTGRES_USER: ${POSTGRES_USER:-postgres}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-postgres}
+      POSTGRES_DB: ${POSTGRES_DB:-postgres}
+    ports:
+      - "${POSTGRES_PORT:-5432}:5432"
+    volumes:
+      - postgres-data:/var/lib/postgresql
+
+volumes:
+  postgres-data: