feat: PostgreSQL image with TimescaleDB, VectorChord, pgvector

- Multi-stage Dockerfile for optimized image size (676MB vs 2GB)
- Support for PostgreSQL 15, 16, 17, 18
- TimescaleDB 2.24.0, VectorChord 1.0.0, pgvector 0.8.1
- Auto-creation of extensions on first startup
- CI/CD with tests for all versions
- OCI labels and healthcheck included

init-extensions.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+set -e
+
+psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" <<-EOSQL
+    CREATE EXTENSION IF NOT EXISTS timescaledb CASCADE;
+    CREATE EXTENSION IF NOT EXISTS vector;
+    CREATE EXTENSION IF NOT EXISTS vchord CASCADE;
+EOSQL
+
+echo "Extensions timescaledb, vector, and vchord have been created."