test: 13 Integration-Tests hinzugefügt + .gitignore optimiert

Integration-Tests:
- test_help_flag, test_version_flag
- test_dry_run_no_changes, test_actual_rename
- test_hidden_files_preserved, test_hidden_file_with_spaces
- test_umlaut_conversion, test_double_extension
- test_exclude_pattern, test_quiet_mode
- test_multiple_paths, test_parentheses_removed
- test_special_identifiers_preserved

.gitignore:
- Besser organisiert (Kategorien)
- Cargo.lock hinzugefügt
- Temporäre Dateien (*.tmp, *.log, *.bak)
- OS-spezifische Dateien (Thumbs.db)
- Test-Artefakte

Gesamt: 22 Tests (9 Unit + 13 Integration)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,29 @@
+# Rust / Cargo
+/target
+**/*.rs.bk
+Cargo.lock
+*.pdb
+
+# IDEs
+.idea/
+.vscode/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Project-specific
+info/
+CLAUDE.md
+
+# Test artifacts
+/test/testverzeichnis
+
+# Temporary files
+*.tmp
+*.log
+*.bak
+