fix: smart next-free room number suggestion

- Placeholder shows next free after global max (e.g. 204 if 203 is max)
- Error message suggests next free starting from typed+1:
  type 101 (taken) → suggests 102
  type 201 (taken) → suggests 202
  type 1011 (taken) → suggests 1012
- Suggestion is a clickable link that auto-fills the field

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/rooms/RoomModal.tsx

@@ -127,21 +127,31 @@ export function RoomModal({ open, room, existingNumbers = [], categories = [], o
     setPhotoIdx(p => Math.max(0, p - 1))
   }
 
-  // Find next available room number (skips existing ones)
-  const nextFreeNumber = (() => {
-    if (isEdit) return null
+  const numberTaken = !isEdit && !!form.number && existingNumbers.includes(form.number)
+
+  // Find next available room number starting from a given base
+  const findNextFree = (base: number): string => {
     const taken = new Set(existingNumbers)
-    // Try incrementing from the highest existing number
-    const nums = existingNumbers
-      .map(n => parseInt(n))
-      .filter(n => !isNaN(n))
-      .sort((a, b) => a - b)
-    let candidate = (nums[nums.length - 1] ?? 100) + 1
+    let candidate = base
     while (taken.has(String(candidate))) candidate++
     return String(candidate)
+  }
+
+  // Placeholder for empty field: next free after current max
+  const placeholderNumber = (() => {
+    if (isEdit) return null
+    const nums = existingNumbers.map(n => parseInt(n)).filter(n => !isNaN(n))
+    const max = nums.length > 0 ? Math.max(...nums) : 100
+    return findNextFree(max + 1)
   })()
 
-  const numberTaken = !isEdit && !!form.number && existingNumbers.includes(form.number)
+  // Suggestion when typed number is taken: increment from typed+1
+  const nextFreeNumber = (() => {
+    if (!numberTaken) return null
+    const typedNum = parseInt(form.number)
+    if (isNaN(typedNum)) return null
+    return findNextFree(typedNum + 1)
+  })()
 
   const handleSave = () => {
     if (!form.number || numberTaken) return
@@ -233,12 +243,15 @@ export function RoomModal({ open, room, existingNumbers = [], categories = [], o
               <input
                 type="text"
                 className={cn('input', numberTaken && 'border-red-400 focus:ring-red-400')}
-                placeholder={nextFreeNumber ?? '101'}
+                placeholder={placeholderNumber ?? '101'}
                 value={form.number}
                 onChange={e => set('number', e.target.value)}
               />
               {numberTaken && (
-                <p className="text-xs text-red-500 mt-1">Номер {form.number} уже существует{nextFreeNumber ? `. Следующий свободный: ${nextFreeNumber}` : ''}</p>
+                <p className="text-xs text-red-500 mt-1">
+                  Номер {form.number} уже занят
+                  {nextFreeNumber ? <> — следующий свободный: <button type="button" className="underline font-medium" onClick={() => set('number', nextFreeNumber)}>{nextFreeNumber}</button></> : ''}
+                </p>
               )}
             </div>
             <div>