feat(web): persist list-page filters in URL search params

Resources, projects, and allocations filter state now syncs to/from
URL so filters survive refresh and can be shared via link.
Text inputs are debounced (300ms) to avoid URL churn.

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

apps/web/src/hooks/useUrlFilters.ts

@@ -0,0 +1,59 @@
+"use client";
+
+import { useRouter, useSearchParams, usePathname } from "next/navigation";
+import { useCallback, useRef, useTransition } from "react";
+
+// Typed-routes are enabled in next.config.ts; bypass for dynamic URLs.
+type PlainRouter = { replace: (url: string, opts?: { scroll?: boolean }) => void };
+
+/**
+ * Syncs a filter object with URL search params.
+ * T must be a flat record of string | undefined values.
+ *
+ * - Reads current filter values from URL search params, falling back to `defaults`.
+ * - Returns a stable `setFilters` updater that writes to the URL via `router.replace`
+ *   (no back-button history entry per keystroke).
+ * - Default values are NOT written to the URL, keeping URLs clean and shareable.
+ */
+export function useUrlFilters<T extends Record<string, string | undefined>>(
+  defaults: T,
+): [T, (updates: Partial<T>) => void] {
+  const searchParams = useSearchParams();
+  const router = useRouter() as unknown as PlainRouter;
+  const pathname = usePathname();
+  const [, startTransition] = useTransition();
+
+  // Stable ref so setFilters doesn't need defaults in its deps array.
+  const defaultsRef = useRef(defaults);
+  defaultsRef.current = defaults;
+
+  // Read current values from URL, falling back to defaults
+  const filters = Object.fromEntries(
+    Object.keys(defaults).map((key) => {
+      const val = searchParams.get(key);
+      return [key, val ?? defaults[key]];
+    }),
+  ) as T;
+
+  const setFilters = useCallback(
+    (updates: Partial<T>) => {
+      const params = new URLSearchParams(searchParams.toString());
+      const defs = defaultsRef.current;
+
+      for (const [key, value] of Object.entries(updates)) {
+        if (value === undefined || value === defs[key as keyof T]) {
+          params.delete(key); // Clean URL — don't show default values
+        } else {
+          params.set(key, String(value));
+        }
+      }
+
+      startTransition(() => {
+        router.replace(`${pathname}?${params.toString()}`, { scroll: false });
+      });
+    },
+    [searchParams, router, pathname],
+  );
+
+  return [filters, setFilters];
+}