feat: implement dashboard ban overview (Stage 5)

- Add ban_service reading fail2ban SQLite DB via read-only aiosqlite
- Add geo_service resolving IPs via ip-api.com with 10k in-memory cache
- Add GET /api/dashboard/bans and GET /api/dashboard/accesses endpoints
- Add TimeRange, DashboardBanItem, DashboardBanListResponse, AccessListItem,
  AccessListResponse models in models/ban.py
- Build BanTable component (Fluent UI DataGrid) with bans/accesses modes,
  pagination, loading/error/empty states, and ban-count badges
- Build useBans hook managing time-range and pagination state
- Update DashboardPage: status bar + time-range toolbar + tab switcher
- Add 37 new backend tests (ban service, geo service, dashboard router)
- All 141 tests pass; ruff/mypy --strict/tsc --noEmit clean

frontend/src/hooks/useBans.ts

@@ -0,0 +1,107 @@
+/**
+ * `useBans` hook.
+ *
+ * Fetches and manages paginated ban-list or access-list data from the
+ * dashboard endpoints.  Re-fetches automatically when `timeRange` or `page`
+ * changes.
+ */
+
+import { useCallback, useEffect, useRef, useState } from "react";
+import { fetchAccesses, fetchBans } from "../api/dashboard";
+import type { AccessListItem, DashboardBanItem, TimeRange } from "../types/ban";
+
+/** The dashboard view mode: aggregate bans or individual access events. */
+export type BanTableMode = "bans" | "accesses";
+
+/** Items per page for the ban/access tables. */
+const PAGE_SIZE = 100;
+
+/** Return value shape for {@link useBans}. */
+export interface UseBansResult {
+  /** Ban items — populated when `mode === "bans"`, otherwise empty. */
+  banItems: DashboardBanItem[];
+  /** Access items — populated when `mode === "accesses"`, otherwise empty. */
+  accessItems: AccessListItem[];
+  /** Total records in the selected time window (for pagination). */
+  total: number;
+  /** Current 1-based page number. */
+  page: number;
+  /** Navigate to a specific page. */
+  setPage: (p: number) => void;
+  /** Whether a fetch is currently in flight. */
+  loading: boolean;
+  /** Error message if the last fetch failed, otherwise `null`. */
+  error: string | null;
+  /** Imperatively re-fetch the current page. */
+  refresh: () => void;
+}
+
+/**
+ * Fetch and manage dashboard ban-list or access-list data.
+ *
+ * Automatically re-fetches when `mode`, `timeRange`, or `page` changes.
+ *
+ * @param mode      - `"bans"` for the ban-list view; `"accesses"` for the
+ *   access-list view.
+ * @param timeRange - Time-range preset that controls how far back to look.
+ * @returns Current data, pagination state, loading flag, and a `refresh`
+ *   callback.
+ */
+export function useBans(mode: BanTableMode, timeRange: TimeRange): UseBansResult {
+  const [banItems, setBanItems] = useState<DashboardBanItem[]>([]);
+  const [accessItems, setAccessItems] = useState<AccessListItem[]>([]);
+  const [total, setTotal] = useState<number>(0);
+  const [page, setPage] = useState<number>(1);
+  const [loading, setLoading] = useState<boolean>(true);
+  const [error, setError] = useState<string | null>(null);
+
+  // Reset page when mode or time range changes.
+  useEffect(() => {
+    setPage(1);
+  }, [mode, timeRange]);
+
+  const doFetch = useCallback(async (): Promise<void> => {
+    setLoading(true);
+    setError(null);
+    try {
+      if (mode === "bans") {
+        const data = await fetchBans(timeRange, page, PAGE_SIZE);
+        setBanItems(data.items);
+        setAccessItems([]);
+        setTotal(data.total);
+      } else {
+        const data = await fetchAccesses(timeRange, page, PAGE_SIZE);
+        setAccessItems(data.items);
+        setBanItems([]);
+        setTotal(data.total);
+      }
+    } catch (err: unknown) {
+      setError(err instanceof Error ? err.message : "Failed to fetch data");
+    } finally {
+      setLoading(false);
+    }
+  }, [mode, timeRange, page]);
+
+  // Stable ref to the latest doFetch so the refresh callback is always current.
+  const doFetchRef = useRef(doFetch);
+  doFetchRef.current = doFetch;
+
+  useEffect(() => {
+    void doFetch();
+  }, [doFetch]);
+
+  const refresh = useCallback((): void => {
+    void doFetchRef.current();
+  }, []);
+
+  return {
+    banItems,
+    accessItems,
+    total,
+    page,
+    setPage,
+    loading,
+    error,
+    refresh,
+  };
+}