Add weekday selection for weekly recurrence and fix RRULE generation

- Add weekday selection UI for weekly recurring events with checkboxes
- Implement BYDAY parameter generation in RRULE based on selected days
- Fix missing RRULE generation in iCalendar output
- Convert reminder durations to proper EventReminder structs
- Add responsive CSS styling for weekday selection interface

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

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

src/components/create_event_modal.rs

@@ -87,6 +87,7 @@ pub struct EventCreationData {
     pub categories: String, // Comma-separated list
     pub reminder: ReminderType,
     pub recurrence: RecurrenceType,
+    pub recurrence_days: Vec<bool>, // [Sun, Mon, Tue, Wed, Thu, Fri, Sat] for weekly recurrence
 }
 
 impl Default for EventCreationData {
@@ -112,6 +113,7 @@ impl Default for EventCreationData {
             categories: String::new(),
             reminder: ReminderType::default(),
             recurrence: RecurrenceType::default(),
+            recurrence_days: vec![false; 7], // [Sun, Mon, Tue, Wed, Thu, Fri, Sat] - all false by default
         }
     }
 }
@@ -290,11 +292,29 @@ pub fn create_event_modal(props: &CreateEventModalProps) -> Html {
                     "yearly" => RecurrenceType::Yearly,
                     _ => RecurrenceType::None,
                 };
+                // Reset recurrence days when changing recurrence type
+                data.recurrence_days = vec![false; 7];
                 event_data.set(data);
             }
         })
     };
 
+    let on_weekday_change = {
+        let event_data = event_data.clone();
+        move |day_index: usize| {
+            let event_data = event_data.clone();
+            Callback::from(move |e: Event| {
+                if let Some(input) = e.target_dyn_into::<HtmlInputElement>() {
+                    let mut data = (*event_data).clone();
+                    if day_index < data.recurrence_days.len() {
+                        data.recurrence_days[day_index] = input.checked();
+                        event_data.set(data);
+                    }
+                }
+            })
+        }
+    };
+
     let on_start_date_change = {
         let event_data = event_data.clone();
         Callback::from(move |e: Event| {
@@ -601,6 +621,35 @@ pub fn create_event_modal(props: &CreateEventModalProps) -> Html {
                             </select>
                         </div>
                     </div>
+
+                    // Show weekday selection only when weekly recurrence is selected
+                    if matches!(data.recurrence, RecurrenceType::Weekly) {
+                        <div class="form-group">
+                            <label>{"Repeat on"}</label>
+                            <div class="weekday-selection">
+                                {
+                                    ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"]
+                                        .iter()
+                                        .enumerate()
+                                        .map(|(i, day)| {
+                                            let day_checked = data.recurrence_days.get(i).cloned().unwrap_or(false);
+                                            let on_change = on_weekday_change(i);
+                                            html! {
+                                                <label key={i} class="weekday-checkbox">
+                                                    <input 
+                                                        type="checkbox" 
+                                                        checked={day_checked}
+                                                        onchange={on_change}
+                                                    />
+                                                    <span class="weekday-label">{day}</span>
+                                                </label>
+                                            }
+                                        })
+                                        .collect::<Html>()
+                                }
+                            </div>
+                        </div>
+                    }
                 </div>
                 
                 <div class="modal-footer">