MidnightNameplates Phase 9.3.8 - Preview Alignment Polish

Focused only on preview composition and spacing.

Changes:
- Entire preview stack moved slightly lower.
- Removed cast-icon compensation that shifted the complete mock-up off center.
- Name sits closer to the health bar.
- Cast bar centered directly beneath the health bar.
- Cast icon attached cleanly to the left edge.
- Cast timer anchored cleanly inside the right edge.
- Aura rows centered over the nameplate and tightened vertically.
- Preview note moved closer to the preview.
- Small breathing-room adjustment between preview and the active options page.
- Reset button now says Reset Phase 9.
- Real in-game nameplate size and runtime logic unchanged.

Test:
1. /mnp opens cleanly.
2. Auras, name, health bar, cast bar and timer share one visual centerline.
3. Cast icon no longer drags the whole preview to the side.
4. GENERAL heading no longer touches the preview frame.
5. All pages and scrollbars still work.
6. No Lua errors.
