feat(client): show git-describe version next to the brand logo

Display the app version (output of `git describe --tags`) in the header
beside the gitmost logo: a clean tag renders as `vX.Y.Z`, otherwise the
tag plus commits-since and short hash (e.g. v0.90.1-56-g25975acd).

- vite.config.ts: resolve APP_VERSION from env (Docker/CI) -> git describe
  (local) -> package.json version fallback
- app-header.tsx: render APP_VERSION after the brand block (ml="md"),
  nudge the Home nav group (ml={50} -> "xl")
- Dockerfile: accept APP_VERSION build-arg in the builder stage (.git is
  excluded from the build context)
- CI: pass APP_VERSION build-arg — release.yml uses the tag, develop.yml
  computes git describe with fetch-depth: 0
- nx.json: add APP_VERSION to the build target inputs so the cache
  invalidates when the version changes

apps/client/vite.config.ts

@@ -1,9 +1,28 @@
 import { defineConfig, loadEnv } from "vite";
 import react from "@vitejs/plugin-react";
 import * as path from "path";
+import { execSync } from "node:child_process";
 
 const envPath = path.resolve(process.cwd(), "..", "..");
 
+// Resolve the version string shown in the UI.
+// Priority: explicit APP_VERSION env (injected by Docker/CI, where .git is absent),
+// then `git describe` for local builds, then the package.json version as a fallback.
+function resolveAppVersion(cwd: string): string {
+  const fromEnv = process.env.APP_VERSION?.trim();
+  if (fromEnv) return fromEnv;
+  try {
+    return execSync("git describe --tags --always", {
+      cwd,
+      stdio: ["ignore", "pipe", "ignore"],
+    })
+      .toString()
+      .trim();
+  } catch {
+    return `v${process.env.npm_package_version ?? "0.0.0"}`;
+  }
+}
+
 export default defineConfig(({ mode }) => {
   const {
     APP_URL,
@@ -32,7 +51,7 @@ export default defineConfig(({ mode }) => {
         POSTHOG_HOST,
         POSTHOG_KEY,
       },
-      APP_VERSION: JSON.stringify(process.env.npm_package_version),
+      APP_VERSION: JSON.stringify(resolveAppVersion(envPath)),
     },
     plugins: [react()],
     build: {