Add share target, prompt templates, command palette and session organisation

- PWA share target: shared text/links start a new chat or go into a
  recent session (chooser dialog)
- Prompt templates (personal + global for admins) with {{placeholders}}
  that are asked for on insert; managed under Settings → Templates
- Ctrl/Cmd+K command palette; Alt+N new session, Alt+Up/Down switch
  sessions, Ctrl+, settings
- Sessions can be pinned, archived and filed into folders; the list can
  be grouped by date or by project, groups are collapsible
- Fix: the "What's new" dialog was never shown to signed-in users

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/components/settings/Templates.tsx

@@ -0,0 +1,79 @@
+import { useEffect, useState } from "react";
+import { confirmDialog, toast } from "../../dialogs";
+import { useT } from "../../i18n";
+import { loadTemplates, placeholders, saveTemplates, type Template, type TemplateLists } from "../../templates";
+import { Icon } from "../Icon";
+
+function List({ scope, initial }: { scope: "personal" | "global"; initial: Template[] }) {
+  const t = useT();
+  const [list, setList] = useState<Template[]>(initial);
+  const [dirty, setDirty] = useState(false);
+  const set = (i: number, patch: Partial<Template>) => {
+    setList((l) => l.map((x, j) => (j === i ? { ...x, ...patch } : x)));
+    setDirty(true);
+  };
+  const save = () =>
+    saveTemplates(scope, list.filter((x) => x.name.trim() || x.text.trim()))
+      .then((l) => (setList(l), setDirty(false), toast(t("settings.saved"), "success")))
+      .catch((e) => toast(e.message));
+  const remove = async (i: number) => {
+    if (!(await confirmDialog({ message: t("templates.deleteConfirm", { name: list[i].name || "?" }), danger: true, confirmLabel: t("common.delete") }))) return;
+    setList((l) => l.filter((_, j) => j !== i));
+    setDirty(true);
+  };
+
+  return (
+    <div className="panel">
+      <h3>
+        <Icon name={scope === "global" ? "users" : "user"} /> {t(scope === "global" ? "templates.globalTitle" : "templates.personalTitle")}
+      </h3>
+      <div className="hint" style={{ marginBottom: 10 }}>
+        {t(scope === "global" ? "templates.globalHint" : "templates.personalHint")}
+      </div>
+      {list.map((x, i) => (
+        <div key={x.id || `new${i}`} className="tpl-edit">
+          <div className="row">
+            <input className="grow" value={x.name} placeholder={t("templates.name")} onChange={(e) => set(i, { name: e.target.value })} />
+            <button className="ghost small" onClick={() => remove(i)} aria-label={t("common.delete")}>
+              <Icon name="trash" />
+            </button>
+          </div>
+          <textarea rows={4} value={x.text} placeholder={t("templates.textPlaceholder")} onChange={(e) => set(i, { text: e.target.value })} />
+          {placeholders(x.text).length > 0 && (
+            <div className="tpl-ph">
+              {placeholders(x.text).map((p) => (
+                <span key={p.name} className="chip">
+                  {p.name}
+                </span>
+              ))}
+            </div>
+          )}
+        </div>
+      ))}
+      <div className="row" style={{ marginTop: 8 }}>
+        <button onClick={() => (setList([...list, { id: "", name: "", text: "" }]), setDirty(true))}>
+          <Icon name="plus" /> {t("templates.add")}
+        </button>
+        <span className="grow" />
+        <button className="primary" disabled={!dirty} onClick={save}>
+          {t("common.save")}
+        </button>
+      </div>
+    </div>
+  );
+}
+
+/** Prompt templates: personal ones and (admins) the ones every user sees. */
+export function Templates() {
+  const [lists, setLists] = useState<TemplateLists>();
+  useEffect(() => {
+    loadTemplates().then(setLists).catch((e) => toast(e.message));
+  }, []);
+  if (!lists) return null;
+  return (
+    <>
+      <List scope="personal" initial={lists.personal} />
+      {lists.can_edit_global && <List scope="global" initial={lists.global} />}
+    </>
+  );
+}