Initial commit: Complete CalDAV calendar synchronizer

- Rust-based CLI tool for Zoho to Nextcloud calendar sync
- Selective calendar import from Zoho to single Nextcloud calendar
- Timezone-aware event handling for next-week synchronization
- Comprehensive configuration system with TOML support
- CLI interface with debug, list, and sync operations
- Complete documentation and example configurations

config/default.toml

@@ -0,0 +1,54 @@
+# Default CalDAV Sync Configuration
+# This file provides default values for the Zoho to Nextcloud calendar sync
+
+# Zoho Configuration (Source)
+[zoho]
+server_url = "https://caldav.zoho.com/caldav"
+username = ""
+password = ""
+selected_calendars = []
+
+# Nextcloud Configuration (Target)  
+[nextcloud]
+server_url = ""
+username = ""
+password = ""
+target_calendar = "Imported-Zoho-Events"
+create_if_missing = true
+
+[server]
+# Request timeout in seconds
+timeout = 30
+
+[calendar]
+# Calendar color in hex format
+color = "#3174ad"
+# Default timezone for processing
+timezone = "UTC"
+
+[sync]
+# Synchronization interval in seconds (300 = 5 minutes)
+interval = 300
+# Whether to perform synchronization on startup
+sync_on_startup = true
+# Number of weeks ahead to sync
+weeks_ahead = 1
+# Whether to run in dry-run mode (preview changes only)
+dry_run = false
+
+# Performance settings
+max_retries = 3
+retry_delay = 5
+
+# Optional filtering configuration
+# [filters]
+# # Event types to include (leave empty for all)
+# event_types = ["meeting", "appointment"]
+# # Keywords to filter events by
+# keywords = ["work", "meeting", "project"]
+# # Keywords to exclude
+# exclude_keywords = ["personal", "holiday", "cancelled"]
+# # Minimum event duration in minutes
+# min_duration_minutes = 5
+# # Maximum event duration in hours
+# max_duration_hours = 24