MidnightNameplates 0.11.0.5 - Blizzard Plate Suppression Hardening

ROOT CAUSE
- Blizzard can restore/reapply UnitFrame alpha after our initial suppression.
- This can happen during target, threat, cast and other nameplate visual updates.
- Result: portions of the Blizzard nameplate intermittently appear through the Midnight plate.

FIX
- Persistent secure post-hooks on Blizzard UnitFrame SetAlpha and Show.
- MidnightNameplates reasserts alpha=0 only when Hide Blizzard plate visuals is enabled.
- Delayed 0 / 0.05 / 0.20 second suppression passes after plate suppression.
- RefreshPlate reasserts suppression after all Midnight presentation work.
- Target/focus/threat transitions trigger a suppression re-check.
- Restore path still returns Blizzard UnitFrame alpha to 1 when suppression is disabled.
- No Blizzard anchors, protected attributes, or secure layout state are modified.

TEST
1. Keep "Hide Blizzard plate visuals" ON.
2. Fight a crowded pack.
3. Change target repeatedly.
4. Let mobs gain/lose threat.
5. Watch casts start/stop.
6. No Blizzard health/name/cast presentation should bleed through.
7. Toggle Hide Blizzard plate visuals OFF: Blizzard presentation should return.
8. Toggle it ON again: only Midnight presentation should remain.
9. Classification visibility and stacking from 11.0.4 must still work.
10. Friendly-player auras and profile/import-export systems must still work.
11. No Lua/taint/secret-value errors.
