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.

TODO.md

@@ -25,7 +25,7 @@
 - [✔️] Basic UI (I went with tview)
 - [✔️] Save / Load Database
 - [✔️] Schemas / Domains / Tables
-- [ ] Add Relations
+- [✔️] Add Relations
 - [ ] Add Indexes
 - [ ] Add Views
 - [ ] Add Sequences
@@ -34,7 +34,7 @@
 
 ## Documentation
 
-- [ ] API documentation (godoc)
+- [✔️] API documentation (godoc)
 - [ ] Usage examples for each format combination
 
 ## Advanced Features