feat(filters): "Share view" link button in the sidebar

Add a share button next to Clear all that copies a link reproducing the current
filter view (filters, sort, scope) to the clipboard, with a confirmation toast.
This is the opt-in replacement for the old always-on URL mirroring. Trilingual.

frontend/src/components/Sidebar.tsx

@@ -10,6 +10,7 @@ import {
   Pencil,
   RefreshCw,
   RotateCcw,
+  Share2,
   X,
 } from "lucide-react";
 import {
@@ -33,6 +34,8 @@ import {
   type SidebarLayout,
   type WidgetId,
 } from "../lib/sidebarLayout";
+import { shareUrl } from "../lib/urlState";
+import { notify } from "../lib/notifications";
 
 // Filter ids; display labels resolved at render time via t("sidebar.sort.<id>") etc.
 const SORT_IDS = [
@@ -196,6 +199,15 @@ export default function Sidebar({
     (dateActive ? 1 : 0);
   const active = activeCount > 0;
 
+  async function shareView() {
+    try {
+      await navigator.clipboard.writeText(shareUrl(filters));
+      notify({ message: t("sidebar.shareCopied") });
+    } catch {
+      notify({ level: "warning", message: t("sidebar.shareFailed") });
+    }
+  }
+
   function clearAll() {
     setCustomDates(false);
     setFilters({ ...DEFAULT_SIDEBAR_FILTERS, q: filters.q, scope: filters.scope });
@@ -486,6 +498,16 @@ export default function Sidebar({
               {t("sidebar.clearAll")}
             </button>
           )}
+          {!editing && (
+            <button
+              onClick={shareView}
+              title={t("sidebar.shareView")}
+              aria-label={t("sidebar.shareView")}
+              className="p-1.5 rounded-lg text-muted hover:text-fg hover:bg-card transition"
+            >
+              <Share2 className="w-4 h-4" />
+            </button>
+          )}
           {editing && (
             <button
               onClick={() => setLayout({ ...DEFAULT_LAYOUT })}