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/src/routes/calendar/+page.svelte

@@ -136,7 +136,7 @@
 </script>
 
 <svelte:head>
-	<title>{$t('adventures.visit_calendar')} - AdventureLog</title>
+	<title>{$t('adventures.visit_calendar')} - Voyage</title>
 </svelte:head>
 
 <div class="min-h-screen bg-gradient-to-br from-base-200 via-base-100 to-base-200">