Add Prettier for TypeScript formatting

- Install prettier
- Configure .prettierrc.json and .prettierignore
- Add npm scripts: format, format:check
- Add Makefile target: format-frontend
- Format all frontend files

frontend/app/admin/availability/page.tsx

@@ -8,7 +8,13 @@ import { Header } from "../../components/Header";
 import { useRequireAuth } from "../../hooks/useRequireAuth";
 import { components } from "../../generated/api";
 import constants from "../../../../shared/constants.json";
-import { formatDate, formatDisplayDate, getDateRange, formatTimeString, isWeekend } from "../../utils/date";
+import {
+  formatDate,
+  formatDisplayDate,
+  getDateRange,
+  formatTimeString,
+  isWeekend,
+} from "../../utils/date";
 
 const { slotDurationMinutes, maxAdvanceDays, minAdvanceDays } = constants.booking;
 
@@ -57,14 +63,14 @@ export default function AdminAvailabilityPage() {
   const fetchAvailability = useCallback(async () => {
     const dateRange = getDateRange(minAdvanceDays, maxAdvanceDays);
     if (!dateRange.length) return;
-    
+
     try {
       const fromDate = formatDate(dateRange[0]);
       const toDate = formatDate(dateRange[dateRange.length - 1]);
       const data = await api.get<AvailabilityResponse>(
         `/api/admin/availability?from=${fromDate}&to=${toDate}`
       );
-      
+
       const map = new Map<string, TimeSlot[]>();
       for (const day of data.days) {
         map.set(day.date, day.slots);
@@ -118,21 +124,21 @@ export default function AdminAvailabilityPage() {
 
   const saveAvailability = async () => {
     if (!selectedDate) return;
-    
+
     setIsSaving(true);
     setError(null);
-    
+
     try {
       const slots = editSlots.map((s) => ({
         start_time: s.start_time + ":00",
         end_time: s.end_time + ":00",
       }));
-      
+
       await api.put("/api/admin/availability", {
         date: formatDate(selectedDate),
         slots,
       });
-      
+
       await fetchAvailability();
       closeModal();
     } catch (err) {
@@ -144,16 +150,16 @@ export default function AdminAvailabilityPage() {
 
   const clearAvailability = async () => {
     if (!selectedDate) return;
-    
+
     setIsSaving(true);
     setError(null);
-    
+
     try {
       await api.put("/api/admin/availability", {
         date: formatDate(selectedDate),
         slots: [],
       });
-      
+
       await fetchAvailability();
       closeModal();
     } catch (err) {
@@ -186,16 +192,16 @@ export default function AdminAvailabilityPage() {
 
   const executeCopy = async () => {
     if (!copySource || copyTargets.size === 0) return;
-    
+
     setIsCopying(true);
     setError(null);
-    
+
     try {
       await api.post("/api/admin/availability/copy", {
         source_date: copySource,
         target_dates: Array.from(copyTargets),
       });
-      
+
       await fetchAvailability();
       cancelCopyMode();
     } catch (err) {
@@ -236,10 +242,12 @@ export default function AdminAvailabilityPage() {
             </div>
             {copySource && (
               <div style={styles.copyActions}>
-                <span style={styles.copyHint}>
-                  Select days to copy to, then click Copy
-                </span>
-                <button onClick={executeCopy} disabled={copyTargets.size === 0 || isCopying} style={styles.copyButton}>
+                <span style={styles.copyHint}>Select days to copy to, then click Copy</span>
+                <button
+                  onClick={executeCopy}
+                  disabled={copyTargets.size === 0 || isCopying}
+                  style={styles.copyButton}
+                >
                   {isCopying ? "Copying..." : `Copy to ${copyTargets.size} day(s)`}
                 </button>
                 <button onClick={cancelCopyMode} style={styles.cancelButton}>
@@ -249,9 +257,7 @@ export default function AdminAvailabilityPage() {
             )}
           </div>
 
-          {error && !selectedDate && (
-            <div style={styles.errorBanner}>{error}</div>
-          )}
+          {error && !selectedDate && <div style={styles.errorBanner}>{error}</div>}
 
           <div style={styles.calendar}>
             {dates.map((date) => {
@@ -318,9 +324,7 @@ export default function AdminAvailabilityPage() {
       {selectedDate && (
         <div style={styles.modalOverlay} onClick={closeModal}>
           <div style={styles.modal} onClick={(e) => e.stopPropagation()}>
-            <h2 style={styles.modalTitle}>
-              Edit Availability - {formatDisplayDate(selectedDate)}
-            </h2>
+            <h2 style={styles.modalTitle}>Edit Availability - {formatDisplayDate(selectedDate)}</h2>
 
             {error && <div style={styles.modalError}>{error}</div>}
 
@@ -333,7 +337,9 @@ export default function AdminAvailabilityPage() {
                     style={styles.timeSelect}
                   >
                     {TIME_OPTIONS.map((t) => (
-                      <option key={t} value={t}>{t}</option>
+                      <option key={t} value={t}>
+                        {t}
+                      </option>
                     ))}
                   </select>
                   <span style={styles.slotDash}>→</span>
@@ -343,7 +349,9 @@ export default function AdminAvailabilityPage() {
                     style={styles.timeSelect}
                   >
                     {TIME_OPTIONS.map((t) => (
-                      <option key={t} value={t}>{t}</option>
+                      <option key={t} value={t}>
+                        {t}
+                      </option>
                     ))}
                   </select>
                   <button
@@ -629,4 +637,3 @@ const pageStyles: Record<string, React.CSSProperties> = {
 };
 
 const styles = { ...sharedStyles, ...pageStyles };
-