MidnightNameplates 0.9.0 - Phase 9 NPC & Spell Rule Engine Foundation

This phase deliberately establishes the runtime/data layer before the large visual editor.

Implemented:
- Persistent NPC rule database.
- Persistent spell rule database.
- Exact name matching with WoW 12.1 secret-value guards.
- NPC overrides: scale, alpha, health color, frame color.
- Spell overrides: cast color, cast border color, emphasis flag.
- Rules are applied after normal Unit Type / Classification styling, so a specific rule wins.
- Rules config page with master enable and rule counts.
- AddNPCRule(name) and AddSpellRule(name) APIs ready for the Phase 9.1 visual editor.

Next Phase 9.1:
- Full visual NPC/Spell Rule Manager.
- Add/edit/delete/duplicate rules.
- Search/filter.
- Priority controls.
- Live preview/editor.
- No Lua scripting required.
