chore: complete ManaCore → Mana rename (docs, go modules, plists, images)

Final cleanup of references missed in previous rename commits:

- Dockerfiles: PUBLIC_MANA_CORE_AUTH_URL → PUBLIC_MANA_AUTH_URL
- Go modules: github.com/manacore/* → github.com/mana/* (7 go.mod files)
- launchd plists: com.manacore.* → com.mana.* (14 files renamed + content)
- Image assets: *_Manacore_AI_Credits* → *_Mana_AI_Credits* (11 files)
- .env.example files: ManaCore brand strings → Mana
- .prettierignore: stale apps/manacore/* paths → apps/mana/*
- Markdown docs (CLAUDE.md, /docs/*): mana-core-auth → mana-auth, etc.

Excluded from rename: .claude/, devlog/, manascore/ (historical content),
client testimonials, blueprints, npm package refs (@mana-core/*).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/mac-mini/notifications.env.example

@@ -1,4 +1,4 @@
-# ManaCore Notification Configuration
+# Mana Notification Configuration
 # Copy this file to the project root as .env.notifications
 # cp scripts/mac-mini/notifications.env.example .env.notifications
 
@@ -23,7 +23,7 @@ TELEGRAM_CHAT_ID=
 EMAIL_TO=
 
 # From address (optional)
-EMAIL_FROM=manacore@mana.how
+EMAIL_FROM=mana@mana.how
 
 # Note: For email to work, install and configure msmtp on Mac Mini:
 #   brew install msmtp