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/voyage.txt

@@ -0,0 +1,7 @@
+ █████╗ ██████╗ ██╗   ██╗███████╗███╗   ██╗████████╗██╗   ██╗██████╗ ███████╗██╗      ██████╗  ██████╗ 
+██╔══██╗██╔══██╗██║   ██║██╔════╝████╗  ██║╚══██╔══╝██║   ██║██╔══██╗██╔════╝██║     ██╔═══██╗██╔════╝ 
+███████║██║  ██║██║   ██║█████╗  ██╔██╗ ██║   ██║   ██║   ██║██████╔╝█████╗  ██║     ██║   ██║██║  ███╗
+██╔══██║██║  ██║╚██╗ ██╔╝██╔══╝  ██║╚██╗██║   ██║   ██║   ██║██╔══██╗██╔══╝  ██║     ██║   ██║██║   ██║
+██║  ██║██████╔╝ ╚████╔╝ ███████╗██║ ╚████║   ██║   ╚██████╔╝██║  ██║███████╗███████╗╚██████╔╝╚██████╔╝
+╚═╝  ╚═╝╚═════╝   ╚═══╝  ╚══════╝╚═╝  ╚═══╝   ╚═╝    ╚═════╝ ╚═╝  ╚═╝╚══════╝╚══════╝ ╚═════╝  ╚═════╝ 
+“Go confidently in the direction of your dreams! Live the life you've imagined.” ― Henry David Thoreau