Fix singleton to series conversion with complete RRULE parameter support

- Add new context menu callback for singleton events to avoid series pipeline
- Implement complete RRULE construction with INTERVAL, COUNT, and UNTIL parameters
- Update frontend service methods to pass recurrence parameters correctly
- Add missing recurrence fields to backend UpdateEventRequest model
- Fix parameter ordering in frontend method calls
- Ensure singleton→series conversion uses single event pipeline initially

This resolves issues where converting singleton events to recurring series
would not respect recurrence interval (every N days), count (N occurrences),
or until date parameters.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

backend/src/handlers/events.rs

@@ -762,6 +762,8 @@ pub async fn update_event(
         .ok_or_else(|| ApiError::NotFound(format!("Event with UID '{}' not found", request.uid)))?;
 
     // Parse dates and times as local times (no UTC conversion)
+    println!("🕐 UPDATE: Received start_date: '{}', start_time: '{}', timezone: '{}'", 
+             request.start_date, request.start_time, request.timezone);
     let start_datetime =
         parse_event_datetime_local(&request.start_date, &request.start_time, request.all_day)
             .map_err(|e| ApiError::BadRequest(format!("Invalid start date/time: {}", e)))?;
@@ -828,6 +830,99 @@ pub async fn update_event(
 
     event.priority = request.priority;
 
+    // Process recurrence information to set RRULE
+    println!("🔄 Processing recurrence: '{}'", request.recurrence);
+    println!("🔄 Recurrence days: {:?}", request.recurrence_days);
+    println!("🔄 Recurrence interval: {:?}", request.recurrence_interval);
+    println!("🔄 Recurrence count: {:?}", request.recurrence_count);
+    println!("🔄 Recurrence end date: {:?}", request.recurrence_end_date);
+    
+    let rrule = if request.recurrence.starts_with("FREQ=") {
+        // Frontend sent a complete RRULE string, use it directly
+        if request.recurrence.is_empty() {
+            None
+        } else {
+            Some(request.recurrence.clone())
+        }
+    } else {
+        // Parse recurrence type and build RRULE with all parameters
+        let base_rrule = match request.recurrence.to_uppercase().as_str() {
+            "DAILY" => Some("FREQ=DAILY".to_string()),
+            "WEEKLY" => {
+                // Handle weekly recurrence with optional BYDAY parameter
+                let mut rrule = "FREQ=WEEKLY".to_string();
+
+                // Check if specific days are selected (recurrence_days has 7 elements: [Sun, Mon, Tue, Wed, Thu, Fri, Sat])
+                if request.recurrence_days.len() == 7 {
+                    let selected_days: Vec<&str> = request
+                        .recurrence_days
+                        .iter()
+                        .enumerate()
+                        .filter_map(|(i, &selected)| {
+                            if selected {
+                                Some(match i {
+                                    0 => "SU", // Sunday
+                                    1 => "MO", // Monday
+                                    2 => "TU", // Tuesday
+                                    3 => "WE", // Wednesday
+                                    4 => "TH", // Thursday
+                                    5 => "FR", // Friday
+                                    6 => "SA", // Saturday
+                                    _ => return None,
+                                })
+                            } else {
+                                None
+                            }
+                        })
+                        .collect();
+
+                    if !selected_days.is_empty() {
+                        rrule = format!("{};BYDAY={}", rrule, selected_days.join(","));
+                    }
+                }
+
+                Some(rrule)
+            }
+            "MONTHLY" => Some("FREQ=MONTHLY".to_string()),
+            "YEARLY" => Some("FREQ=YEARLY".to_string()),
+            "NONE" | "" => None, // Clear any existing recurrence
+            _ => None,
+        };
+
+        // Add INTERVAL, COUNT, and UNTIL parameters if specified
+        if let Some(mut rrule_string) = base_rrule {
+            // Add INTERVAL parameter (every N days/weeks/months/years)
+            if let Some(interval) = request.recurrence_interval {
+                if interval > 1 {
+                    rrule_string = format!("{};INTERVAL={}", rrule_string, interval);
+                }
+            }
+
+            // Add COUNT or UNTIL parameter (but not both - COUNT takes precedence)
+            if let Some(count) = request.recurrence_count {
+                rrule_string = format!("{};COUNT={}", rrule_string, count);
+            } else if let Some(end_date) = &request.recurrence_end_date {
+                // Convert YYYY-MM-DD to YYYYMMDD format for UNTIL
+                if let Ok(date) = chrono::NaiveDate::parse_from_str(end_date, "%Y-%m-%d") {
+                    rrule_string = format!("{};UNTIL={}", rrule_string, date.format("%Y%m%d"));
+                }
+            }
+
+            Some(rrule_string)
+        } else {
+            None
+        }
+    };
+
+    event.rrule = rrule.clone();
+    println!("🔄 Set event RRULE to: {:?}", rrule);
+    
+    if rrule.is_some() {
+        println!("✨ Converting singleton event to recurring series with RRULE: {}", rrule.as_ref().unwrap());
+    } else {
+        println!("📝 Event remains non-recurring (no RRULE set)");
+    }
+
     // Update the event on the CalDAV server
     println!(
         "📝 Updating event {} at calendar_path: {}, event_href: {}",

backend/src/handlers/series.rs

@@ -229,6 +229,8 @@ pub async fn update_event_series(
         "🔄 Update event series request received: series_uid='{}', update_scope='{}', recurrence_count={:?}, recurrence_end_date={:?}",
         request.series_uid, request.update_scope, request.recurrence_count, request.recurrence_end_date
     );
+    println!("🕐 SERIES: Received start_date: '{}', start_time: '{}', timezone: '{}'", 
+             request.start_date, request.start_time, request.timezone);
 
     // Extract and verify token
     let token = extract_bearer_token(&headers)?;
@@ -963,6 +965,8 @@ async fn update_single_occurrence(
     // Update the modified properties from the request
     exception_event.dtstart = start_datetime;
     exception_event.dtend = Some(end_datetime);
+    exception_event.dtstart_tzid = Some(request.timezone.clone());
+    exception_event.dtend_tzid = Some(request.timezone.clone());
     exception_event.summary = if request.title.trim().is_empty() {
         existing_event.summary.clone() // Keep original if empty
     } else {

backend/src/models.rs

@@ -147,6 +147,9 @@ pub struct UpdateEventRequest {
     pub reminder: String,              // reminder type
     pub recurrence: String,            // recurrence type
     pub recurrence_days: Vec<bool>,    // [Sun, Mon, Tue, Wed, Thu, Fri, Sat] for weekly recurrence
+    pub recurrence_interval: Option<u32>, // Every N days/weeks/months/years
+    pub recurrence_count: Option<u32>, // Number of occurrences
+    pub recurrence_end_date: Option<String>, // When the series ends (YYYY-MM-DD)
     pub calendar_path: Option<String>, // Optional - search all calendars if not specified
     pub update_action: Option<String>, // "update_series" for recurring events
     pub timezone: String,              // Client timezone (e.g., "+05:00", "-04:00")