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

frontend/package.json

@@ -1,5 +1,5 @@
 {
-	"name": "adventurelog-frontend",
+	"name": "voyage-frontend",
 	"version": "0.12.0",
 	"scripts": {
 		"dev": "vite dev",