Rename AdventureLog to Voyage and add fork attribution

- Replace all AdventureLog references with Voyage across ~102 files
  (7 case variants: AdventureLog, adventurelog, Adventurelog, ADVENTURELOG,
  AdventUrelog, AdventureLOG, adventure-log, adventure_log)
- Rename brand, static, and documentation assets to use voyage naming
- Rename install_adventurelog.sh → install_voyage.sh
- Update README.md and voyage_overview.md to credit AdventureLog as
  the upstream project and Sean Morley as its original creator

.github/workflows/cdn-beta.yml

@@ -12,7 +12,7 @@ on:
       - "cdn/**"
 
 env:
-  IMAGE_NAME: "adventurelog-cdn"
+  IMAGE_NAME: "voyage-cdn"
 
 jobs:
   upload: