Add terminal client, memory, model fallback, version and install improvements

- codecraft: full-screen terminal client (ratatui) – local tools and files,
  models via the CodeCraft server gateway or own providers (standalone with a
  guided setup), slash commands, @files, permission dialogs, resume, update
- Static Linux CLI builds (x86_64/aarch64, cargo-zigbuild) served by the
  server: /cli/install.sh and /cli/download/<target>
- Project memory (remember tool, .codecraft/memory.md) and personal memory
- Model fallback when a host is unreachable or a budget is used up
- Version/commit in UI and health, daily release check, "What's new" dialog
- PWA: install button, maskable icon, manifest id and screenshots
- Case-insensitive detection of connection errors for retries

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

web/src/components/WhatsNew.tsx

@@ -0,0 +1,46 @@
+import { useState } from "react";
+import { getLang, useT } from "../i18n";
+import { WHATS_NEW } from "../whatsnew";
+import { Icon } from "./Icon";
+
+const KEY = "codecraft.seenVersion";
+
+/** Shown once after the server was updated to a version with release notes. */
+export function WhatsNew({ version }: { version: string }) {
+  const t = useT();
+  const seen = localStorage.getItem(KEY);
+  const [open, setOpen] = useState(() => {
+    // First visit ever: just remember the version.
+    if (!seen) {
+      localStorage.setItem(KEY, version);
+      return false;
+    }
+    return seen !== version && !!WHATS_NEW[version];
+  });
+  if (!open) return null;
+  const entry = WHATS_NEW[version];
+  const items = getLang() === "de" ? entry.de : entry.en;
+  const close = () => {
+    localStorage.setItem(KEY, version);
+    setOpen(false);
+  };
+  return (
+    <div className="modal-backdrop" onClick={close}>
+      <div className="modal" role="dialog" aria-label={t("whatsnew.title")} onClick={(e) => e.stopPropagation()}>
+        <h3>
+          <Icon name="sparkle" /> {t("whatsnew.title", { version })}
+        </h3>
+        <ul className="whatsnew">
+          {items.map((i) => (
+            <li key={i}>{i}</li>
+          ))}
+        </ul>
+        <div className="row" style={{ justifyContent: "flex-end" }}>
+          <button className="primary" onClick={close}>
+            {t("common.ok")}
+          </button>
+        </div>
+      </div>
+    </div>
+  );
+}