Graph: rework annotation creation - only custom-sized boxes with full text support

[4rkad]

Bug + Enhancement

Several issues with annotation boxes in the transaction graph, plus a UX improvement proposal.

Current problems

1. Single-click creates unwanted boxes
In annotation mode, every single click on the canvas creates a default-sized annotation box. This easily fills the screen with empty boxes by accident.

2. Default box: text overflows on confirm
When creating a box with a single click and entering a moderately long comment, pressing Enter causes the body text to overflow outside the box boundaries.

3. Custom-sized box (click-and-drag): only supports title
When creating an annotation box by click-and-drag, only the title field is available (~20 characters). There is no option to add body/comment text.

Proposed behavior

• Remove single-click annotation creation. Only allow click-and-drag to create annotation boxes (custom size). This prevents accidental box spam.
• Custom-sized boxes should support both title (optional) and body text, same as the current single-click box but without the overflow issue.
• Text must stay contained within the box boundaries, wrapping as needed.

Steps to reproduce

1. Open the graph explorer
2. Enter annotation mode
3. Single-click multiple times on the canvas → screen fills with empty boxes
4. Create a default box, enter a long comment, press Enter → text overflows
5. Click-and-drag to create a custom box → only title available, no body text

[Copexit]

Reopened: the fix for this issue was reverted in commit 3198c04 after review found it wasn't working correctly. Needs a dedicated session.