feat(ui): add relationship management features in schema editor

- Implement functionality to create, update, delete, and view relationships between tables.
- Introduce new UI screens for managing relationships, including forms for adding and editing relationships.
- Enhance table editor with navigation to relationship management.
- Ensure relationships are displayed in a structured table format for better usability.

pkg/pgsql/doc.go

@@ -0,0 +1,36 @@
+// Package pgsql provides PostgreSQL-specific utilities and helpers.
+//
+// # Overview
+//
+// The pgsql package contains PostgreSQL-specific functionality including:
+//   - SQL reserved keyword validation
+//   - Data type mappings and conversions
+//   - PostgreSQL-specific schema introspection helpers
+//
+// # Components
+//
+// keywords.go - SQL reserved keywords validation
+//
+//	Provides functions to check if identifiers conflict with SQL reserved words
+//	and need quoting for safe usage in PostgreSQL queries.
+//
+// datatypes.go - PostgreSQL data type utilities
+//
+//	Contains mappings between PostgreSQL data types and their equivalents in other
+//	systems, as well as type conversion and normalization functions.
+//
+// # Usage
+//
+//	// Check if identifier needs quoting
+//	if pgsql.IsReservedKeyword("user") {
+//	    // Quote the identifier
+//	}
+//
+//	// Normalize data type
+//	normalizedType := pgsql.NormalizeDataType("varchar(255)")
+//
+// # Purpose
+//
+// This package supports the PostgreSQL reader and writer implementations by providing
+// shared utilities for handling PostgreSQL-specific schema elements and constraints.
+package pgsql