Clean up unused code and compiler warnings

Removed unused functions and variables identified after RRULE parameter fix:
- Remove unused build_series_rrule function from backend series handler
- Remove unused RecurrenceType::from_rrule and helper functions from frontend
- Prefix unused state variables with underscores to suppress warnings

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

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

backend/src/handlers/series.rs

@@ -460,34 +460,6 @@ pub async fn delete_event_series(
 
 // Helper functions
 
-fn build_series_rrule(request: &CreateEventSeriesRequest) -> Result<String, ApiError> {
-    // Extract frequency from request
-    let recurrence_freq = if request.recurrence.contains("FREQ=") {
-        // Parse RRULE to extract frequency
-        if request.recurrence.contains("FREQ=DAILY") {
-            "daily"
-        } else if request.recurrence.contains("FREQ=WEEKLY") {
-            "weekly"
-        } else if request.recurrence.contains("FREQ=MONTHLY") {
-            "monthly"
-        } else if request.recurrence.contains("FREQ=YEARLY") {
-            "yearly"
-        } else {
-            return Err(ApiError::BadRequest("Invalid RRULE frequency".to_string()));
-        }
-    } else {
-        let lower = request.recurrence.to_lowercase();
-        match lower.as_str() {
-            "daily" => "daily",
-            "weekly" => "weekly",
-            "monthly" => "monthly", 
-            "yearly" => "yearly",
-            _ => return Err(ApiError::BadRequest("Invalid recurrence type".to_string())),
-        }
-    };
-    
-    build_series_rrule_with_freq(request, recurrence_freq)
-}
 
 fn build_series_rrule_with_freq(request: &CreateEventSeriesRequest, freq: &str) -> Result<String, ApiError> {
     let mut rrule_parts = Vec::new();

frontend/src/app.rs

@@ -54,9 +54,9 @@ pub fn App() -> Html {
     let calendar_context_menu_date = use_state(|| -> Option<NaiveDate> { None });
     let create_event_modal_open = use_state(|| false);
     let selected_date_for_event = use_state(|| -> Option<NaiveDate> { None });
-    let recurring_edit_modal_open = use_state(|| false);
+    let _recurring_edit_modal_open = use_state(|| false);
-    let recurring_edit_event = use_state(|| -> Option<VEvent> { None });
+    let _recurring_edit_event = use_state(|| -> Option<VEvent> { None });
-    let recurring_edit_data = use_state(|| -> Option<EventCreationData> { None });
+    let _recurring_edit_data = use_state(|| -> Option<EventCreationData> { None });
     
     // Calendar view state - load from localStorage if available
     let current_view = use_state(|| {

frontend/src/components/create_event_modal.rs

@@ -81,17 +81,6 @@ impl Default for RecurrenceType {
     }
 }
 
-impl RecurrenceType {
-    pub fn from_rrule(rrule: Option<&str>) -> Self {
-        match rrule {
-            Some(rule) if rule.contains("FREQ=DAILY") => RecurrenceType::Daily,
-            Some(rule) if rule.contains("FREQ=WEEKLY") => RecurrenceType::Weekly,
-            Some(rule) if rule.contains("FREQ=MONTHLY") => RecurrenceType::Monthly,
-            Some(rule) if rule.contains("FREQ=YEARLY") => RecurrenceType::Yearly,
-            _ => RecurrenceType::None,
-        }
-    }
-}
 
 /// Parse RRULE string into recurrence components
 /// Example RRULE: "FREQ=WEEKLY;INTERVAL=2;BYDAY=MO,WE,FR;UNTIL=20231215T000000Z"
@@ -763,7 +752,7 @@ pub fn create_event_modal(props: &CreateEventModalProps) -> Html {
         })
     };
 
-    let on_priority_input = {
+    let _on_priority_input = {
         let event_data = event_data.clone();
         Callback::from(move |e: InputEvent| {
             if let Some(input) = e.target_dyn_into::<HtmlInputElement>() {

frontend/src/services/calendar_service.rs

@@ -866,34 +866,6 @@ impl CalendarService {
     }
 
 
-    /// Calculate next weekday occurrence for WEEKLY frequency with BYDAY
-    fn next_weekday_occurrence(current_date: NaiveDate, byday: &str, interval: i32) -> NaiveDate {
-        let weekdays = Self::parse_byday(byday);
-        if weekdays.is_empty() {
-            return current_date + Duration::weeks(interval as i64);
-        }
-
-        let current_weekday = current_date.weekday();
-        
-        // Find next occurrence within current week
-        let mut next_occurrences = Vec::new();
-        for &target_weekday in &weekdays {
-            let days_until = Self::days_until_weekday(current_weekday, target_weekday);
-            if days_until > 0 {
-                next_occurrences.push((days_until, target_weekday));
-            }
-        }
-        
-        // Sort by days_until and return the closest one
-        if !next_occurrences.is_empty() {
-            next_occurrences.sort_by_key(|(days, _)| *days);
-            return current_date + Duration::days(next_occurrences[0].0 as i64);
-        }
-        
-        // No more occurrences this week, move to next interval
-        let next_week_start = current_date + Duration::weeks(interval as i64) - Duration::days(current_weekday.num_days_from_monday() as i64);
-        next_week_start + Duration::days(weekdays[0].num_days_from_monday() as i64)
-    }
 
     /// Parse BYDAY parameter (e.g., "MO,WE,FR" -> [Monday, Wednesday, Friday])
     fn parse_byday(byday: &str) -> Vec<Weekday> {
@@ -912,19 +884,6 @@ impl CalendarService {
             .collect()
     }
 
-    /// Calculate days until target weekday
-    fn days_until_weekday(from: Weekday, to: Weekday) -> i32 {
-        let from_num = from.num_days_from_monday();
-        let to_num = to.num_days_from_monday();
-        
-        if to_num > from_num {
-            (to_num - from_num) as i32
-        } else if to_num < from_num {
-            (7 + to_num - from_num) as i32
-        } else {
-            0 // Same day
-        }
-    }
 
     /// Add months to a date (handling month boundary issues)
     fn add_months(date: NaiveDate, months: i32) -> Option<NaiveDate> {