[aaqilniz]

Description

LoopBack applications previously returned generic database-specific error responses or raw SQLSTATE codes for PostgreSQL failures. This PR introduces a PostgreSQL error normalization module (lib/normalize-error.js) that intercepts raw PostgreSQL driver errors and maps them to standard, protocol-neutral domain codes using 5-character SQLSTATE codes.

Error Code Mappings

PostgreSQL SQLSTATE	Condition / Error Name	Normalized Domain Code
23505	unique_violation	UNIQUE_CONSTRAINT_VIOLATION
42P01	undefined_table	TABLE_NOT_FOUND
42703	undefined_column	COLUMN_NOT_FOUND
23503	foreign_key_violation	FOREIGN_KEY_VIOLATION
23502	not_null_violation	NOT_NULL_VIOLATION
23514	check_violation	CHECK_CONSTRAINT_VIOLATED
22P02, 22001, 22003	Invalid text representation / Data exceptions	DATA_TYPE_MISMATCH
40P01, 40001	Deadlock / Serialization failure	LOCK_CONFLICT
08000, 08003, 08006	Connection exceptions	CONNECTION_FAILURE
N/A (Lifecycle)	Inactive or closed transaction usage	TRANSACTION_NOT_ACTIVE

Depends on PR#11645

Checklist

• DCO (Developer Certificate of Origin) signed in all commits
• npm test passes on your machine
• New tests added or existing tests modified to cover all changes
• Code conforms with the style guide
• Commit messages are following our guidelines