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/readers/doc.go

@@ -0,0 +1,53 @@
+// Package readers provides interfaces and implementations for reading database schemas
+// from various input formats and data sources.
+//
+// # Overview
+//
+// The readers package defines a common Reader interface that all format-specific readers
+// implement. This allows RelSpec to read database schemas from multiple sources including:
+//   - Live databases (PostgreSQL, SQLite)
+//   - Schema definition files (DBML, DCTX, DrawDB, GraphQL)
+//   - ORM model files (GORM, Bun, Drizzle, Prisma, TypeORM)
+//   - Data interchange formats (JSON, YAML)
+//
+// # Architecture
+//
+// Each reader implementation is located in its own subpackage (e.g., pkg/readers/dbml,
+// pkg/readers/pgsql) and implements the Reader interface, supporting three levels of
+// granularity:
+//   - ReadDatabase() - Read complete database with all schemas
+//   - ReadSchema() - Read single schema with all tables
+//   - ReadTable() - Read single table with all columns and metadata
+//
+// # Usage
+//
+// Readers are instantiated with ReaderOptions containing source-specific configuration:
+//
+//	// Read from file
+//	reader := dbml.NewReader(&readers.ReaderOptions{
+//	    FilePath: "schema.dbml",
+//	})
+//	db, err := reader.ReadDatabase()
+//
+//	// Read from database
+//	reader := pgsql.NewReader(&readers.ReaderOptions{
+//	    ConnectionString: "postgres://user:pass@localhost/mydb",
+//	})
+//	db, err := reader.ReadDatabase()
+//
+// # Supported Formats
+//
+//   - dbml: Database Markup Language files
+//   - dctx: DCTX schema files
+//   - drawdb: DrawDB JSON format
+//   - graphql: GraphQL schema definition language
+//   - json: JSON database schema
+//   - yaml: YAML database schema
+//   - gorm: Go GORM model structs
+//   - bun: Go Bun model structs
+//   - drizzle: TypeScript Drizzle ORM schemas
+//   - prisma: Prisma schema language
+//   - typeorm: TypeScript TypeORM entities
+//   - pgsql: PostgreSQL live database introspection
+//   - sqlite: SQLite database files
+package readers