Show blocklist import error badge in navigation

When the most recent scheduled import completed with errors, surface the
failure in the persistent app shell:
- A warning MessageBar appears at top of main content area
- An amber badge is rendered on the Blocklists sidebar nav item

Backend: add last_run_errors: bool | None to ScheduleInfo model and
populate it in get_schedule_info() from the latest import_log row.

Frontend: extend ScheduleInfo type, add useBlocklistStatus polling hook,
wire both indicators into MainLayout.

Tests: 3 new service tests + 1 new router test (433 total, all pass).

frontend/src/hooks/useBlocklist.ts

@@ -235,3 +235,51 @@ export function useRunImport(): UseRunImportReturn {
 
   return { running, lastResult, error, runNow };
 }
+
+// ---------------------------------------------------------------------------
+// useBlocklistStatus
+// ---------------------------------------------------------------------------
+
+/** How often to re-check the schedule endpoint for import errors (ms). */
+const BLOCKLIST_POLL_INTERVAL_MS = 60_000;
+
+export interface UseBlocklistStatusReturn {
+  /** `true` when the most recent import run completed with errors. */
+  hasErrors: boolean;
+}
+
+/**
+ * Poll `GET /api/blocklists/schedule` every 60 seconds to detect whether
+ * the most recent blocklist import had errors.
+ *
+ * Network failures during polling are silently ignored — the indicator
+ * simply retains its previous value until the next successful poll.
+ */
+export function useBlocklistStatus(): UseBlocklistStatusReturn {
+  const [hasErrors, setHasErrors] = useState(false);
+
+  useEffect(() => {
+    let cancelled = false;
+
+    const poll = (): void => {
+      fetchSchedule()
+        .then((info) => {
+          if (!cancelled) {
+            setHasErrors(info.last_run_errors === true);
+          }
+        })
+        .catch(() => {
+          // Silently swallow network errors — do not change indicator state.
+        });
+    };
+
+    poll();
+    const id = window.setInterval(poll, BLOCKLIST_POLL_INTERVAL_MS);
+    return (): void => {
+      cancelled = true;
+      window.clearInterval(id);
+    };
+  }, []);
+
+  return { hasErrors };
+}

frontend/src/layouts/MainLayout.tsx

@@ -8,6 +8,7 @@
 
 import { useCallback, useEffect, useState } from "react";
 import {
+  Badge,
   Button,
   makeStyles,
   mergeClasses,
@@ -31,6 +32,7 @@ import {
 import { NavLink, Outlet, useNavigate } from "react-router-dom";
 import { useAuth } from "../providers/AuthProvider";
 import { useServerStatus } from "../hooks/useServerStatus";
+import { useBlocklistStatus } from "../hooks/useBlocklist";
 
 // ---------------------------------------------------------------------------
 // Styles
@@ -100,6 +102,12 @@ const useStyles = makeStyles({
     flexGrow: 1,
   },
 
+  navLinkContent: {
+    display: "flex",
+    alignItems: "center",
+    gap: tokens.spacingHorizontalS,
+    flexGrow: 1,
+  },
   navLink: {
     display: "flex",
     alignItems: "center",
@@ -199,6 +207,7 @@ export function MainLayout(): React.JSX.Element {
   // with the icon-only sidebar rather than the full-width one.
   const [collapsed, setCollapsed] = useState(() => window.innerWidth < 640);
   const { status } = useServerStatus();
+  const { hasErrors: blocklistHasErrors } = useBlocklistStatus();
 
   /** True only after the first successful poll and fail2ban is unreachable. */
   const serverOffline = status !== null && !status.online;
@@ -249,32 +258,45 @@ export function MainLayout(): React.JSX.Element {
 
         {/* Nav links */}
         <ul className={styles.navList} role="list" aria-label="Pages">
-          {NAV_ITEMS.map((item) => (
-            <li key={item.to} role="listitem">
-              <Tooltip
-                content={collapsed ? item.label : ""}
-                relationship="label"
-                positioning="after"
-              >
-                <NavLink
-                  to={item.to}
-                  end={item.end}
-                  className={({ isActive }) =>
-                    mergeClasses(
-                      styles.navLink,
-                      isActive && styles.navLinkActive,
-                    )
-                  }
-                  aria-label={collapsed ? item.label : undefined}
+          {NAV_ITEMS.map((item) => {
+            const showBadge = item.to === "/blocklists" && blocklistHasErrors;
+            return (
+              <li key={item.to} role="listitem">
+                <Tooltip
+                  content={collapsed ? item.label : ""}
+                  relationship="label"
+                  positioning="after"
                 >
-                  {item.icon}
-                  {!collapsed && (
-                    <Text className={styles.navLabel}>{item.label}</Text>
-                  )}
-                </NavLink>
-              </Tooltip>
-            </li>
-          ))}
+                  <NavLink
+                    to={item.to}
+                    end={item.end}
+                    className={({ isActive }) =>
+                      mergeClasses(
+                        styles.navLink,
+                        isActive && styles.navLinkActive,
+                      )
+                    }
+                    aria-label={collapsed ? item.label : undefined}
+                  >
+                    <span className={styles.navLinkContent}>
+                      {item.icon}
+                      {!collapsed && (
+                        <Text className={styles.navLabel}>{item.label}</Text>
+                      )}
+                    </span>
+                    {showBadge && (
+                      <Badge
+                        appearance="filled"
+                        color="warning"
+                        size="extra-small"
+                        aria-label="Import errors"
+                      />
+                    )}
+                  </NavLink>
+                </Tooltip>
+              </li>
+            );
+          })}
         </ul>
 
         {/* Footer — Logout */}
@@ -313,6 +335,18 @@ export function MainLayout(): React.JSX.Element {
             </MessageBar>
           </div>
         )}
+        {/* Blocklist import error warning — shown when the last scheduled import had errors */}
+        {blocklistHasErrors && (
+          <div className={styles.warningBar} role="alert">
+            <MessageBar intent="warning">
+              <MessageBarBody>
+                <MessageBarTitle>Blocklist Import Errors</MessageBarTitle>
+                The most recent blocklist import encountered errors. Check the
+                Blocklists page for details.
+              </MessageBarBody>
+            </MessageBar>
+          </div>
+        )}
         <div className={styles.content}>
           <Outlet />
         </div>

frontend/src/types/blocklist.ts

@@ -71,6 +71,8 @@ export interface ScheduleInfo {
   config: ScheduleConfig;
   next_run_at: string | null;
   last_run_at: string | null;
+  /** `true` if the most recent import had errors, `false` if clean, `null` if never run. */
+  last_run_errors: boolean | null;
 }
 
 // ---------------------------------------------------------------------------