MidnightNameplates 0.9.5.4.2 - Friendly Aura Activation & Refresh Fix

FIXED
- Dedicated friendly-player AuraContainer now receives SetUnit before Show.
- Added explicit refresh helper for all visible friendly-player plates.
- Friendly buffs refresh on combat transitions.
- Visibility mode uses a safe combat-state check.
- Existing enemy aura containers remain unchanged.
- Added config help text clarifying that Show Auras + non-OFF visibility are both required.

TEST
1. Unit Types -> Friendly Player -> Show auras ON.
2. Friendly Player Buff Visibility = ALWAYS.
3. Mine only = OFF.
4. Stand next to a buffed friendly player.
5. Buff icons should appear without targeting them.
6. Change visibility to OUT_OF_COMBAT and enter/leave combat.
7. Test IN_COMBAT and OFF.
8. Test icon size/spacing/anchor.
9. Enemy auras remain unchanged.
10. Mailboxes remain filtered.
11. No Lua/taint/secret errors.
