Unify DID input with auto-detection of scope and name

Description

Currently, the DID page uses separate input boxes for scope and name, which can be cumbersome when pasting full DIDs. This issue proposes implementing a single, unified input field that intelligently parses and auto-detects the scope and name components from pasted DIDs.

Current Behavior

• Two separate input fields for scope and name
• Left/right arrow keys switch between fields
• Users must manually split DIDs when pasting

Proposed Solution

• Single input box for DID entry
• Auto-detection logic to parse scope:name format
• Client-side validation with fallback to manual entry if parsing fails
• Remove left/right key navigation between fields

Implementation Details

1. Implement parser for common DID formats (scope:name)
2. Add client-side validation
3. Show inline validation feedback
4. Prompt for manual scope/name entry only when auto-detection fails
5. Preserve backwards compatibility for direct scope/name entry

Acceptance Criteria

• Single input field replaces dual scope/name inputs
• Successfully parses and validates standard DID formats
• Provides clear feedback when validation fails
• Fallback mechanism for manual entry works correctly
• Left/right arrow keys no longer switch between fields
• Unit tests for DID parsing logic

Parent Issue

Part of #621 - [EPIC: Release 39] UX improvements

Parent Issue

• #621

Start at the DID page and trace the existing scope/name inputs, arrow-key navigation, and current validation behavior. Add coverage for DID parsing and verify the unified field, inline errors, manual fallback, backward-compatible entry, and removal of arrow-key switching against the acceptance criteria.