Add sleep tracking, statistics module and backup features

Features:
- Sleep tracking with timer and manual duration input
- Statistics module with 5 tabs (daily summary, feeding, diapers, sleep, growth)
- Export/Import backup functionality in settings
- Complete German, French and Italian translations

.gitignore

@@ -107,3 +107,5 @@ app/release/output-metadata.json
 # Other
 app/src/main/java/it/danieleverducci/lunatracker/TemporaryHardcodedCredentials.kt
 .kotlin/sessions/*
+CLAUDE.md
+.claude/