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/adventures/views/generate_description_view.py

@@ -17,7 +17,7 @@ class GenerateDescription(viewsets.ViewSet):
 
     # User-Agent header required by Wikipedia API, Accept-Language patched in per request
     BASE_HEADERS = {
-        'User-Agent': f'AdventureLog/{getattr(settings, "ADVENTURELOG_RELEASE_VERSION", "unknown")}'
+        'User-Agent': f'Voyage/{getattr(settings, "VOYAGE_RELEASE_VERSION", "unknown")}'
     }
     DEFAULT_LANGUAGE = "en"
     LANGUAGE_PATTERN = re.compile(r"^[a-z0-9-]{2,12}$", re.IGNORECASE)