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

backend/server/run_periodic_sync.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 """
-Periodic sync runner for AdventureLog.
+Periodic sync runner for Voyage.
 Runs sync_visited_regions management command every 60 seconds.
 Managed by supervisord to ensure it inherits container environment variables.
 """