Info page: show the app version, two-column layout on wide screens

An About panel shows the installed version (from Tauri at runtime, since
release builds stamp it at build time; dev builds are labelled as such).
On wide screens the page splits into panels in two columns — card
database, library stats and libraries on the left; sync and about on the
right — while narrow screens keep the single-column order. The sync panel
is now headed "Sync" and the Info page's summary "Library stats".

Closes #22

src/App.tsx

@@ -1,4 +1,5 @@
 import { useEffect, useRef, useState, useCallback, ReactNode } from "react";
+import { getVersion } from "@tauri-apps/api/app";
 import { listen } from "@tauri-apps/api/event";
 import { open } from "@tauri-apps/plugin-dialog";
 import {
@@ -168,10 +169,12 @@ function LibrarySummary({
   ready,
   libStats,
   status,
+  title = "Your library",
 }: {
   ready: boolean;
   libStats: LibraryStats | null;
   status: Status | null;
+  title?: string;
 }) {
   if (!ready) {
     return (
@@ -185,7 +188,7 @@ function LibrarySummary({
     <div className="lib-stats">
       <div className="lib-stats-head">
         <span className="status-dot on" />
-        <span className="lib-stats-title">Your library</span>
+        <span className="lib-stats-title">{title}</span>
       </div>
       {!libStats ? (
         <div className="lib-stats-loading">Loading…</div>
@@ -242,6 +245,12 @@ export default function App() {
   const [status, setStatus] = useState<Status | null>(null);
   const [libStats, setLibStats] = useState<LibraryStats | null>(null);
   const [tab, setTab] = usePersistedState<Tab>("active-tab", "add");
+  // The installed build's version, for the Info page. Release builds stamp
+  // it at build time, so it comes from Tauri rather than package.json.
+  const [appVersion, setAppVersion] = useState<string | null>(null);
+  useEffect(() => {
+    getVersion().then(setAppVersion).catch(() => setAppVersion(null));
+  }, []);
   // A deck a chip elsewhere asked to open; DeckView picks it up and clears it.
   const [openDeckId, setOpenDeckId] = useState<number | null>(null);
   // Deck chips only carry the deck's name, which is unique per library.
@@ -798,41 +807,64 @@ export default function App() {
               // rail it normally sits in is replaced by the bottom nav);
               // on desktop those also appear in the topbar and rail, but sync
               // lives only here.
-              <div className="panel info-panel">
-                <h2 style={{ margin: 0 }}>Card database</h2>
-                <div className="row" style={{ gap: "var(--space-3)", flexWrap: "wrap" }}>
-                  <button className="primary" onClick={updateCardData} disabled={busy}>
-                    {ICON_DOWNLOAD}
-                    {busy ? "Downloading…" : "Update card data"}
-                  </button>
-                  <button onClick={importReferenceDb} disabled={busy}>
-                    {ICON_OPEN_LIBRARY}
-                    Import card data…
-                  </button>
+              // Two columns on wide screens — card data, library stats and the
+              // libraries on the left; sync and the version on the right. On
+              // narrow ones the columns dissolve into one list in the order
+              // set by `.info-*` (see styles.css).
+              <div className="info-grid">
+                <div className="info-col">
+                  <section className="panel info-section info-db">
+                    <h2 style={{ margin: 0 }}>Card database</h2>
+                    <div className="row" style={{ gap: "var(--space-3)", flexWrap: "wrap" }}>
+                      <button className="primary" onClick={updateCardData} disabled={busy}>
+                        {ICON_DOWNLOAD}
+                        {busy ? "Downloading…" : "Update card data"}
+                      </button>
+                      <button onClick={importReferenceDb} disabled={busy}>
+                        {ICON_OPEN_LIBRARY}
+                        Import card data…
+                      </button>
+                    </div>
+                  </section>
+                  <section className="panel info-section info-summary">
+                    <LibrarySummary ready={ready} libStats={libStats} status={status} title="Library stats" />
+                  </section>
+                  <section className="panel info-section info-libraries">
+                    <LibrariesPanel
+                      libraries={libraries}
+                      signedIn={sync?.signed_in ?? false}
+                      onChanged={librariesChanged}
+                    />
+                  </section>
+                </div>
+                <div className="info-col">
+                  <section className="panel info-section info-sync">
+                    {sync === null ? (
+                      <>
+                        <h2 style={{ margin: 0 }}>Sync</h2>
+                        <div className="hint">Checking…</div>
+                      </>
+                    ) : (
+                      <SyncPanel
+                        sync={sync}
+                        setSync={setSync}
+                        syncing={syncing}
+                        runSync={runSync}
+                        onLibraryReplaced={refreshEverything}
+                      />
+                    )}
+                  </section>
+                  <section className="panel info-section info-about">
+                    <h2 style={{ margin: 0 }}>About</h2>
+                    <div className="info-about-row">
+                      <span className="muted">mtgc version</span>
+                      <span className="info-version">
+                        {appVersion ?? "unknown"}
+                        {import.meta.env.DEV && <span className="muted"> · development build</span>}
+                      </span>
+                    </div>
+                  </section>
                 </div>
-                <hr className="deck-section-divider" style={{ margin: 0 }} />
-                <LibrariesPanel
-                  libraries={libraries}
-                  signedIn={sync?.signed_in ?? false}
-                  onChanged={librariesChanged}
-                />
-                <hr className="deck-section-divider" style={{ margin: 0 }} />
-                {sync === null ? (
-                  <>
-                    <h2 style={{ margin: 0 }}>Your library</h2>
-                    <div className="hint">Checking…</div>
-                  </>
-                ) : (
-                  <SyncPanel
-                    sync={sync}
-                    setSync={setSync}
-                    syncing={syncing}
-                    runSync={runSync}
-                    onLibraryReplaced={refreshEverything}
-                  />
-                )}
-                <hr className="deck-section-divider" style={{ margin: 0 }} />
-                <LibrarySummary ready={ready} libStats={libStats} status={status} />
               </div>
             )}
           </div>