Refactor database models to use server defaults for boolean and timestamp fields

- Updated `TimestampMixin` to use `server_default` for `created_at` and `updated_at` fields.
- Modified various models in the `fa_classes`, `doc_types_dig`, `ports`, `units_of_measure`, `invoices`, `parts`, `trailers`, `licenses`, `tenants`, and `user_tenant` modules to set `server_default` for boolean fields and other relevant fields.
- Adjusted the `trailer_types` model to change the schema from `a76` to `public`.
- Implemented database migration execution during application startup in `main.py`.
- Removed old Alembic migration execution logic from the entrypoint script.
- Updated seed data for units of measure and removed unused seed files.

scripts/init_first_time.sh

@@ -530,7 +530,7 @@ if [ $TENANT_QUERY_STATUS -ne 0 ]; then
     echo -e "${RED}✗ Error al consultar el tenant:${NC}"
     echo "$TENANT_ID_RESULT"
     echo -e "${YELLOW}Verificando si la tabla existe...${NC}"
-    docker exec -e PGPASSWORD="${POSTGRES_PASSWORD}" anexo76-postgres-a76 psql -h localhost -p 5432 -U "${POSTGRES_USER}" -d "${POSTGRES_DB}" -c "\dt core.tenants;"
+    exec_pg_sql "\dt core.tenants;"
     exit 1
 fi
 
@@ -540,7 +540,7 @@ if [ -z "$TENANT_ID" ]; then
     echo -e "${RED}✗ Error: No se pudo obtener el ID del tenant${NC}"
     echo "Resultado de la consulta: '$TENANT_ID_RESULT'"
     echo -e "${YELLOW}Intentando ver todos los tenants...${NC}"
-    docker exec -e PGPASSWORD="${POSTGRES_PASSWORD}" anexo76-postgres-a76 psql -h localhost -p 5432 -U "${POSTGRES_USER}" -d "${POSTGRES_DB}" -c "SELECT id, slug FROM core.tenants LIMIT 10;"
+    exec_pg_sql "SELECT id, slug FROM core.tenants LIMIT 10;"
     exit 1
 fi