feat: added sqlc and binded schema.sql as postgresql's init script

sqlc/sqlc.yaml

@@ -0,0 +1,14 @@
+version: "2"
+sql:
+- schema: "../postgresql/schema.sql"
+  queries: "query.sql"
+  engine: "postgresql"
+  gen:
+    go: 
+      out: "../backend/internal/database"
+      sql_package: "pgx/v5"
+  database:
+    # managed: true
+    uri: "postgresql://postgres:postgres@localhost:5432/mydb?sslmode=disable"
+  rules:
+    - sqlc/db-prepare