fix: AdminUserRestrictionsPage - show effective values, auto-remove redundant overrides

Major UX improvements:
- Display effective value in input (override if set, otherwise tier limit)
- Format NULL as "unlimited" (easy to type, no special char needed)
- Auto-remove override when value equals tier default
- "Zurück" button resets to tier default value
- Wider input field (120px) for "unlimited" text

This solves:
- User can now see and edit current effective values
- "unlimited" can be typed and saved
- Redundant overrides (value = tier default) are prevented
- No more confusion with empty fields vs actual values

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

frontend/src/pages/AdminUserRestrictionsPage.jsx

@@ -77,13 +77,7 @@ export default function AdminUserRestrictionsPage() {
 
   function handleChange(featureId, value) {
     const newChanges = { ...changes }
-
-    // Empty string means: remove override
-    if (value === '') {
-      newChanges[featureId] = { action: 'remove', tempValue: '' }
-      setChanges(newChanges)
-      return
-    }
+    const tierLimit = tierLimits[featureId]
 
     // Parse value (EXACTLY like TierLimitsPage)
     let parsedValue = null
@@ -91,6 +85,8 @@ export default function AdminUserRestrictionsPage() {
       parsedValue = null // unlimited
     } else if (value === '0' || value === 'disabled') {
       parsedValue = 0 // disabled
+    } else if (value === '') {
+      parsedValue = null // empty → unlimited
     } else {
       const num = parseInt(value)
       if (!isNaN(num) && num >= 0) {
@@ -100,7 +96,14 @@ export default function AdminUserRestrictionsPage() {
       }
     }
 
-    newChanges[featureId] = { action: 'set', value: parsedValue, tempValue: value }
+    // Check if value equals tier limit → remove override
+    if (parsedValue === tierLimit) {
+      newChanges[featureId] = { action: 'remove', tempValue: value }
+    } else {
+      // Different from tier default → set override
+      newChanges[featureId] = { action: 'set', value: parsedValue, tempValue: value }
+    }
+
     setChanges(newChanges)
   }
 
@@ -175,22 +178,30 @@ export default function AdminUserRestrictionsPage() {
     // Check pending changes first
     if (featureId in changes) {
       const change = changes[featureId]
-      if (change.action === 'remove') return ''
+      if (change.action === 'remove') {
+        // Returning to tier default
+        return formatValue(tierLimits[featureId])
+      }
       if (change.action === 'set') {
         // Use tempValue for display if available, otherwise format the value
         return change.tempValue !== undefined ? change.tempValue : formatValue(change.value)
       }
     }
 
-    // Show existing restriction value (or empty if no restriction)
+    // Show override if exists, otherwise tier limit (= effective value)
     const restriction = restrictions.find(r => r.feature_id === featureId)
-    if (!restriction) return '' // No override = empty input
-    return formatValue(restriction.limit_value)
+    if (restriction) {
+      return formatValue(restriction.limit_value)
+    }
+
+    // No override: show tier limit as default
+    return formatValue(tierLimits[featureId])
   }
 
   function formatValue(val) {
-    if (val === '' || val === null || val === undefined) return ''
-    if (val === '∞' || val === 'unlimited') return '∞'
+    if (val === null || val === undefined) return 'unlimited'
+    if (val === '' ) return ''
+    if (val === '∞' || val === 'unlimited') return 'unlimited'
     if (val === 0 || val === '0') return '0'
     return val.toString()
   }
@@ -258,9 +269,8 @@ export default function AdminUserRestrictionsPage() {
       }}>
         <AlertCircle size={16} style={{ marginTop: 2, flexShrink: 0 }} />
         <div>
-          <strong>Hinweis:</strong> User-Overrides überschreiben Tier-Limits.
-          Leere Felder = kein Override (User nutzt Tier-Standard).
-          Wert eingeben = Override setzen.
+          <strong>Hinweis:</strong> Felder zeigen effektive Werte (Override falls gesetzt, sonst Tier-Standard).
+          Wert ändern → Override wird gesetzt. Wert = Tier-Standard → Override wird entfernt.
         </div>
       </div>
 
@@ -456,9 +466,9 @@ export default function AdminUserRestrictionsPage() {
                                 type="text"
                                 value={displayValue}
                                 onChange={(e) => handleChange(feature.id, e.target.value)}
-                                placeholder="∞"
+                                placeholder=""
                                 style={{
-                                  width: '100px',
+                                  width: '120px',
                                   padding: '6px 8px',
                                   border: `1.5px solid ${changed ? 'var(--accent)' : override ? 'var(--accent)' : 'var(--border)'}`,
                                   borderRadius: 6,
@@ -467,7 +477,7 @@ export default function AdminUserRestrictionsPage() {
                                   fontWeight: override || changed ? 600 : 400,
                                   background: override || changed ? 'var(--accent-light)' : 'var(--bg)',
                                   color: displayValue === '0' ? 'var(--danger)' :
-                                         displayValue === '∞' ? 'var(--accent)' : 'var(--text1)'
+                                         displayValue === 'unlimited' ? 'var(--accent)' : 'var(--text1)'
                                 }}
                               />
                             )}
@@ -477,7 +487,11 @@ export default function AdminUserRestrictionsPage() {
                           <td style={{ padding: '12px 16px', textAlign: 'right' }}>
                             <button
                               className="btn btn-secondary"
-                              onClick={() => handleChange(feature.id, '')}
+                              onClick={() => {
+                                // Reset to tier default
+                                const tierValue = tierLimits[feature.id]
+                                handleChange(feature.id, formatValue(tierValue))
+                              }}
                               disabled={!override}
                               style={{
                                 padding: '4px 8px',
@@ -504,12 +518,16 @@ export default function AdminUserRestrictionsPage() {
             marginTop: 16, padding: 12, background: 'var(--surface2)',
             borderRadius: 8, fontSize: 12, color: 'var(--text3)'
           }}>
-            <strong>Eingabe (Count-Features):</strong>
+            <strong>Eingabe:</strong>
             <div style={{ marginTop: 8, display: 'flex', gap: 16, flexWrap: 'wrap' }}>
-              <span><strong style={{ color: 'var(--accent)' }}>∞</strong> oder <strong>unlimited</strong> = Unbegrenzt</span>
+              <span><strong>unlimited</strong> = Unbegrenzt</span>
               <span><strong style={{ color: 'var(--danger)' }}>0</strong> = Feature deaktiviert</span>
               <span><strong>1+</strong> = Limit-Wert</span>
-              <span><strong>Leer</strong> = kein Override (Tier-Standard)</span>
+            </div>
+            <div style={{ marginTop: 8, fontSize: 11, opacity: 0.8 }}>
+              • Feld zeigt effektiven Wert (Override falls gesetzt, sonst Tier-Standard)<br />
+              • Wert ändern → Override wird gesetzt<br />
+              • Wert = Tier-Standard → Override wird entfernt
             </div>
           </div>
         </>