Merge feat/german-locale: German version, glow effects and search metadata

Brings the German main language (English under /en), the binary glow
effects with the refined drawings and calls to action, and the search
metadata onto the server-side analytics from v2.1.0.

Both sides had added apps/web/proxy.ts. It is now one request shell: it
picks the language and maps the address (routes.ts), and records the page
view server-side (pageview-decision.ts) for every request that is not a
redirect, using the public address the visitor asked for. The browser
analytics component and the /stats proxy route stay removed.

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

apps/web/proxy.ts

@@ -1,8 +1,11 @@
 /**
- * Server request shell. Reads the incoming request once, classifies it via
- * the pure domain decision, and records a page view without touching the
- * response. All analytics happen server-side; no tracking script ships to
- * the browser.
+ * Server request shell. Reads the incoming request once and does two things,
+ * both decided by pure functions in src/domain:
+ *
+ * 1. Picks the language of the request and maps the public address onto the
+ *    app directory (routes.ts).
+ * 2. Records a page view server-side (pageview-decision.ts). No tracking
+ *    script ships to the browser.
  *
  * Page views are browser navigations (`sec-fetch-dest: document`).
  * Router-internal headers (RSC, next-router-prefetch) are stripped by the
@@ -12,7 +15,12 @@
 import { NextResponse, type NextRequest } from "next/server";
 
 import { recordPageviewToUmami } from "@/src/analytics/recordPageviewToUmami";
+import { LOCALE_COOKIE } from "@/src/domain/locale";
 import { decidePageview } from "@/src/domain/pageview-decision";
+import { routeRequest } from "@/src/domain/routes";
+
+const PERMANENT = 308;
+const TEMPORARY = 307;
 
 const primaryLanguage = (acceptLanguage: string | null): string =>
   acceptLanguage?.split(",")[0]?.split(";")[0]?.trim() ?? "";
@@ -22,32 +30,52 @@ const firstForwardedIp = (forwardedFor: string | null): string =>
 
 const hostnameWithoutPort = (host: string): string => host.replace(/:\d+$/, "");
 
-export default function proxy(request: NextRequest): NextResponse {
-  const decision = decidePageview({
-    method: request.method,
-    secFetchDest: request.headers.get("sec-fetch-dest") ?? "",
+export function proxy(request: NextRequest): NextResponse {
+  const route = routeRequest({
     pathname: request.nextUrl.pathname,
-    search: request.nextUrl.search,
-    hostname: hostnameWithoutPort(
-      request.headers.get("x-forwarded-host") ??
-        request.headers.get("host") ??
-        "",
-    ),
-    referrer: request.headers.get("referer") ?? "",
-    language: primaryLanguage(request.headers.get("accept-language")),
-    userAgent: request.headers.get("user-agent") ?? "",
-    clientIp: firstForwardedIp(request.headers.get("x-forwarded-for")),
+    cookie: request.cookies.get(LOCALE_COOKIE)?.value,
+    acceptLanguage: request.headers.get("accept-language"),
   });
 
-  if (decision.track) {
-    recordPageviewToUmami(decision.facts);
+  const url = request.nextUrl.clone();
+  url.pathname = route.to;
+  const response =
+    route.kind === "redirect"
+      ? NextResponse.redirect(url, route.permanent ? PERMANENT : TEMPORARY)
+      : NextResponse.rewrite(url);
+
+  // The answer depends on the visitor's language: caches must keep one per language.
+  if (route.negotiated) {
+    response.headers.append("Vary", "Accept-Language, Cookie");
   }
 
-  return NextResponse.next();
+  // A redirect is not a view: the request that follows it is counted instead.
+  if (route.kind !== "redirect") {
+    const pageview = decidePageview({
+      method: request.method,
+      secFetchDest: request.headers.get("sec-fetch-dest") ?? "",
+      // The public address the visitor asked for, not the internal one it maps to.
+      pathname: request.nextUrl.pathname,
+      search: request.nextUrl.search,
+      hostname: hostnameWithoutPort(
+        request.headers.get("x-forwarded-host") ??
+          request.headers.get("host") ??
+          "",
+      ),
+      referrer: request.headers.get("referer") ?? "",
+      language: primaryLanguage(request.headers.get("accept-language")),
+      userAgent: request.headers.get("user-agent") ?? "",
+      clientIp: firstForwardedIp(request.headers.get("x-forwarded-for")),
+    });
+    if (pageview.track) {
+      recordPageviewToUmami(pageview.facts);
+    }
+  }
+
+  return response;
 }
 
 export const config = {
-  matcher: [
-    "/((?!_next/static|_next/image|.*\\.(?:png|jpe?g|gif|svg|webp|avif|ico|css|mjs|cjs|js|map|txt|xml|json|webmanifest|woff2?|ttf|otf|mp4|webm|mov|pdf|zip)$).*)",
-  ],
+  // Pages only: not Next's own files, the error proxy, or files.
+  matcher: ["/((?!_next/|errors/|.*\\..*).*)"],
 };