fix: update .env from POSTGRES_* to MSSQL_* variables for SQL Server migration

The .env file still had old POSTGRES_* variables which would break local
development and docker compose since config.py now expects MSSQL_* variables.
This matches the variables used in compose.yml and backend/app/core/config.py.

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: Romularques

.env

@@ -31,12 +31,13 @@ SMTP_TLS=True
 SMTP_SSL=False
 SMTP_PORT=587
 
-# Postgres
-POSTGRES_SERVER=localhost
-POSTGRES_PORT=5432
-POSTGRES_DB=app
-POSTGRES_USER=postgres
-POSTGRES_PASSWORD=changethis
+# SQL Server
+MSSQL_SERVER=localhost
+MSSQL_PORT=1433
+MSSQL_DB=app
+MSSQL_USER=sa
+MSSQL_PASSWORD=Changethis1!
+MSSQL_DRIVER=ODBC Driver 18 for SQL Server
 
 SENTRY_DSN=