Fix: prefer IPv4 via gai.conf, revert database.py to simple connection

Fix: use hostaddr param to force IPv4 for psycopg connection

Fix: resolve DB hostname to IPv4 before connecting

Fix: force IPv4 DNS resolution for PostgreSQL connections

Fix: strip whitespace/newlines from env vars

Fix: read env vars at runtime not import time for HF Space secrets

Initial commit — RetailTalk backend for HuggingFace Spaces