Replace hardcoded time slots with dynamic API availability

Both BookingFlow and RescheduleFlow in Appointments.tsx now fetch
from /api/book/availability when a date is selected, matching the
public booking wizard behavior. Loading and error states shown.

- Removed hardcoded availableTimes arrays from both flows
- Added useEffect that fetches availability on date change
- Shows "Checking availability…" while loading
- Shows error message on fetch failure
- Shows "No available slots" when API returns empty

Added tests for RescheduleFlow dynamic slot fetching covering:
loading, fetched slots, error, empty, API params, and re-fetch on
date change.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

src/portal/sections/Appointments.tsx

@@ -573,16 +573,26 @@ export function RescheduleFlow({
   const [submitting, setSubmitting] = useState(false);
   const [error, setError] = useState<string | null>(null);
   const [success, setSuccess] = useState(false);
+  const [slotsLoading, setSlotsLoading] = useState(false);
+  const [slotsError, setSlotsError] = useState<string | null>(null);
+  const [availableTimes, setAvailableTimes] = useState<string[]>([]);
 
-  const availableTimes = [
-    '9:00 AM',
-    '10:00 AM',
-    '11:00 AM',
-    '1:00 PM',
-    '2:00 PM',
-    '3:00 PM',
-    '4:00 PM',
-  ];
+  useEffect(() => {
+    if (!selectedDate || !sessionId) {
+      setAvailableTimes([]);
+      return;
+    }
+    const params = new URLSearchParams({ date: selectedDate });
+    setSlotsLoading(true);
+    setSlotsError(null);
+    fetch(`/api/book/availability?${params.toString()}`, {
+      headers: { "X-Impersonation-Session-Id": sessionId ?? "" },
+    })
+      .then((r) => r.json() as Promise<string[]>)
+      .then(setAvailableTimes)
+      .catch(() => setSlotsError('Failed to load time slots'))
+      .finally(() => setSlotsLoading(false));
+  }, [selectedDate, sessionId]);
 
   async function handleSubmit() {
     if (!selectedDate || !selectedTime) return;
@@ -661,7 +671,12 @@ export function RescheduleFlow({
               />
               {selectedDate && (
                 <div className="grid grid-cols-3 gap-2 mb-4">
-                  {availableTimes.map((time) => (
+                  {slotsLoading && <p className="col-span-3 text-sm text-stone-500 py-2">Checking availability…</p>}
+                  {!slotsLoading && slotsError && <p className="col-span-3 text-sm text-red-500 py-2">{slotsError}</p>}
+                  {!slotsLoading && availableTimes.length === 0 && !slotsError && (
+                    <p className="col-span-3 text-sm text-stone-500 py-2">No available slots on this date.</p>
+                  )}
+                  {!slotsLoading && availableTimes.map((time) => (
                     <button
                       key={time}
                       onClick={() => setSelectedTime(time)}
@@ -723,16 +738,26 @@ function BookingFlow({ onClose, sessionId }: BookingFlowProps) {
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
   const [submitting, setSubmitting] = useState(false);
+  const [slotsLoading, setSlotsLoading] = useState(false);
+  const [slotsError, setSlotsError] = useState<string | null>(null);
+  const [availableTimes, setAvailableTimes] = useState<string[]>([]);
 
-  const availableTimes = [
-    '9:00 AM',
-    '10:00 AM',
-    '11:00 AM',
-    '1:00 PM',
-    '2:00 PM',
-    '3:00 PM',
-    '4:00 PM',
-  ];
+  useEffect(() => {
+    if (!selectedDate || !sessionId) {
+      setAvailableTimes([]);
+      return;
+    }
+    const params = new URLSearchParams({ date: selectedDate });
+    setSlotsLoading(true);
+    setSlotsError(null);
+    fetch(`/api/book/availability?${params.toString()}`, {
+      headers: { "X-Impersonation-Session-Id": sessionId ?? "" },
+    })
+      .then((r) => r.json() as Promise<string[]>)
+      .then(setAvailableTimes)
+      .catch(() => setSlotsError('Failed to load time slots'))
+      .finally(() => setSlotsLoading(false));
+  }, [selectedDate, sessionId]);
 
   useEffect(() => {
     const fetchData = async () => {
@@ -1055,7 +1080,12 @@ function BookingFlow({ onClose, sessionId }: BookingFlowProps) {
                   />
                   {selectedDate && (
                     <div className="grid grid-cols-3 gap-2 mb-4">
-                      {availableTimes.map((time) => (
+                      {slotsLoading && <p className="col-span-3 text-sm text-stone-500 py-2">Checking availability…</p>}
+                      {!slotsLoading && slotsError && <p className="col-span-3 text-sm text-red-500 py-2">{slotsError}</p>}
+                      {!slotsLoading && availableTimes.length === 0 && !slotsError && (
+                        <p className="col-span-3 text-sm text-stone-500 py-2">No available slots on this date.</p>
+                      )}
+                      {!slotsLoading && availableTimes.map((time) => (
                         <button
                           key={time}
                           onClick={() => setSelectedTime(time)}