Add mass unban: DELETE /api/bans/all clears all active bans

- Send fail2ban's `unban --all` command via new `unban_all_ips()` service
  function; returns the count of unbanned IPs
- Add `UnbanAllResponse` Pydantic model (message + count)
- Add `DELETE /api/bans/all` router endpoint; handles 502 on socket error
- Frontend: `bansAll` endpoint constant, `unbanAllBans()` API call,
  `UnbanAllResponse` type, `unbanAll` action in `useActiveBans` hook
- JailsPage: "Clear All Bans" button (visible when bans > 0) with a
  Fluent UI confirmation Dialog before executing the operation
- 7 new tests (3 service, 4 router); 440 total pass, 82% coverage

frontend/src/pages/JailsPage.tsx

@@ -20,6 +20,12 @@ import {
   DataGridHeader,
   DataGridHeaderCell,
   DataGridRow,
+  Dialog,
+  DialogActions,
+  DialogBody,
+  DialogContent,
+  DialogSurface,
+  DialogTitle,
   Field,
   Input,
   MessageBar,
@@ -36,6 +42,7 @@ import {
 import {
   ArrowClockwiseRegular,
   ArrowSyncRegular,
+  DeleteRegular,
   DismissRegular,
   LockClosedRegular,
   LockOpenRegular,
@@ -646,16 +653,38 @@ function BanUnbanForm({ jailNames, onBan, onUnban }: BanUnbanFormProps): React.J
 
 function ActiveBansSection(): React.JSX.Element {
   const styles = useStyles();
-  const { bans, total, loading, error, refresh, unbanIp } = useActiveBans();
+  const { bans, total, loading, error, refresh, unbanIp, unbanAll } = useActiveBans();
   const [opError, setOpError] = useState<string | null>(null);
+  const [opSuccess, setOpSuccess] = useState<string | null>(null);
+  const [confirmOpen, setConfirmOpen] = useState(false);
+  const [clearing, setClearing] = useState(false);
 
   const handleUnban = (ip: string, jail: string): void => {
     setOpError(null);
+    setOpSuccess(null);
     unbanIp(ip, jail).catch((err: unknown) => {
       setOpError(err instanceof Error ? err.message : String(err));
     });
   };
 
+  const handleClearAll = (): void => {
+    setClearing(true);
+    setOpError(null);
+    setOpSuccess(null);
+    unbanAll()
+      .then((res) => {
+        setOpSuccess(res.message);
+        setConfirmOpen(false);
+      })
+      .catch((err: unknown) => {
+        setOpError(err instanceof Error ? err.message : String(err));
+        setConfirmOpen(false);
+      })
+      .finally(() => {
+        setClearing(false);
+      });
+  };
+
   const banColumns = buildBanColumns(handleUnban);
 
   return (
@@ -669,21 +698,81 @@ function ActiveBansSection(): React.JSX.Element {
             </Badge>
           )}
         </Text>
-        <Button
-          size="small"
-          appearance="subtle"
-          icon={<ArrowClockwiseRegular />}
-          onClick={refresh}
-        >
-          Refresh
-        </Button>
+        <div style={{ display: "flex", gap: tokens.spacingHorizontalS }}>
+          <Button
+            size="small"
+            appearance="subtle"
+            icon={<ArrowClockwiseRegular />}
+            onClick={refresh}
+          >
+            Refresh
+          </Button>
+          {total > 0 && (
+            <Button
+              size="small"
+              appearance="outline"
+              icon={<DeleteRegular />}
+              onClick={() => {
+                setConfirmOpen(true);
+              }}
+            >
+              Clear All Bans
+            </Button>
+          )}
+        </div>
       </div>
 
+      {/* Confirmation dialog */}
+      <Dialog
+        open={confirmOpen}
+        onOpenChange={(_ev, data) => {
+          if (!data.open) setConfirmOpen(false);
+        }}
+      >
+        <DialogSurface>
+          <DialogBody>
+            <DialogTitle>Clear All Bans</DialogTitle>
+            <DialogContent>
+              <Text>
+                This will immediately unban <strong>all {String(total)} IP
+                {total !== 1 ? "s" : ""}</strong> across every jail. This
+                action cannot be undone — fail2ban will no longer block any
+                of those addresses until they trigger the rate-limit again.
+              </Text>
+            </DialogContent>
+            <DialogActions>
+              <Button
+                appearance="secondary"
+                onClick={() => {
+                  setConfirmOpen(false);
+                }}
+                disabled={clearing}
+              >
+                Cancel
+              </Button>
+              <Button
+                appearance="primary"
+                onClick={handleClearAll}
+                disabled={clearing}
+                icon={clearing ? <Spinner size="tiny" /> : <DeleteRegular />}
+              >
+                {clearing ? "Clearing…" : "Clear All Bans"}
+              </Button>
+            </DialogActions>
+          </DialogBody>
+        </DialogSurface>
+      </Dialog>
+
       {opError && (
         <MessageBar intent="error">
           <MessageBarBody>{opError}</MessageBarBody>
         </MessageBar>
       )}
+      {opSuccess && (
+        <MessageBar intent="success">
+          <MessageBarBody>{opSuccess}</MessageBarBody>
+        </MessageBar>
+      )}
       {error && (
         <MessageBar intent="error">
           <MessageBarBody>Failed to load bans: {error}</MessageBarBody>