MidnightNameplates 0.10.2.1 - Import/Export UI Polish

UI CHANGES
- Export string moved into a fixed-height internal ScrollFrame.
- Import string moved into a separate fixed-height ScrollFrame.
- Long strings no longer consume the whole Profiles page.
- SELECT ALL button added for export strings.
- CLEAR buttons added for export and import.
- Import preview moved into a compact summary panel.
- Export and Import sections now have clearer separation.
- Main Profiles page scrollbar remains independent.

COPY / PASTE
- Generate Export automatically selects the full string.
- SELECT ALL re-selects the full string.
- Use Ctrl+C to copy and Ctrl+V to paste.

DELETE
- Existing delete confirmation retained unchanged.

TEST
1. Profiles page layout is clean from top to bottom.
2. Generate FULL export: string stays inside compact scroll box.
3. SELECT ALL then Ctrl+C.
4. Paste into Import box with Ctrl+V.
5. PREVIEW IMPORT shows summary.
6. REPLACE import works.
7. Rule MERGE import still works.
8. Main page scrollbar and text-box scrolling do not interfere.
9. Delete confirmation still works.
10. No Lua errors.
