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Excluded from rename: .claude/, devlog/, manascore/ (historical content),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>

services/mana-api-gateway/go.mod

@@ -1,10 +1,10 @@
-module github.com/manacore/mana-api-gateway
+module github.com/mana/mana-api-gateway
 
 go 1.25.0
 
 require (
 	github.com/jackc/pgx/v5 v5.9.1
-	github.com/manacore/shared-go v0.0.0
+	github.com/mana/shared-go v0.0.0
 	github.com/redis/go-redis/v9 v9.18.0
 	github.com/rs/cors v1.11.1
 )
@@ -21,4 +21,4 @@ require (
 	golang.org/x/text v0.29.0 // indirect
 )
 
-replace github.com/manacore/shared-go => ../../packages/shared-go
+replace github.com/mana/shared-go => ../../packages/shared-go