feat(11-04): TenderDetail component with ?tender=<id> wiring

Adds getTender() to the api client and a self-fetching TenderDetail
overlay (pattern: SourceConfigForm) rendering all Tender fields plus a
safe (rel=noopener noreferrer, target=_blank) sourceUrl link. No local
mirroring of Vergabeunterlagen — rawPayload is 100% NULL in the live DB
(research finding), so only the source link exists; NULL value/deadline
render graceful German placeholders (D-05 applies to the detail view too).

page.tsx reads ?tender=<id> via useSearchParams and renders TenderDetail
as an overlay; closing removes the param. ResultsList row clicks set the
param (deviation: ResultsList.tsx was not listed in the plan's
files_modified but is required by the plan's own done-criteria/key_link
"ResultsList-Zeile setzt ?tender=<id>" — Rule 3 auto-fix, blocking).

3/3 TenderDetail tests pass; full web suite (117 tests) and tsc --noEmit
both clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/web/src/app/(portal)/modules/tender-radar/page.tsx

@@ -1,9 +1,11 @@
 'use client';
 
 import { Suspense } from 'react';
+import { useRouter, useSearchParams } from 'next/navigation';
 import { CoverageBanner } from './components/CoverageBanner';
 import { FilterPanel } from './components/FilterPanel';
 import { ResultsList } from './components/ResultsList';
+import { TenderDetail } from './components/TenderDetail';
 
 /**
  * Ausschreibungs-Radar module page within the portal.
@@ -13,16 +15,34 @@ import { ResultsList } from './components/ResultsList';
  * FilterPanel writes filter/sort state into the URL, ResultsList reads it
  * and renders the ~1671 existing DÖE tenders.
  *
- * `useSearchParams()` (used by FilterPanel/ResultsList) requires a
- * Suspense boundary per the Next.js App Router contract — wrapped here
- * even though this component is loaded via `dynamic(..., { ssr: false })`
- * (module-loader.ts), per the plan's explicit Next 16 guidance.
+ * Plan 11-04 (UI-02, D-07): the `?tender=<id>` URL param drives an
+ * in-component detail view (TenderDetail) rendered as an overlay on top
+ * of the list — deliberately NOT a separate Next.js sub-route, since this
+ * page is mounted via `dynamic(..., { ssr: false })` under
+ * `[category]/[moduleSlug]` (Anti-Pattern/Assumption A5). A row click in
+ * ResultsList sets the param; closing the detail removes it.
+ *
+ * `useSearchParams()` (used by FilterPanel/ResultsList/this component)
+ * requires a Suspense boundary per the Next.js App Router contract —
+ * wrapped here even though this component is loaded via
+ * `dynamic(..., { ssr: false })` (module-loader.ts), per the plan's
+ * explicit Next 16 guidance.
  *
  * Intentional hardcoded German strings: full i18n (next-intl message
  * keys) is CONFIG-03, planned for Phase 14 (Research Open Question 3,
  * RESOLVED).
  */
 function TenderRadarContent() {
+  const router = useRouter();
+  const searchParams = useSearchParams();
+  const tenderId = searchParams.get('tender');
+
+  const closeDetail = () => {
+    const next = new URLSearchParams(searchParams.toString());
+    next.delete('tender');
+    router.replace(`?${next.toString()}`);
+  };
+
   return (
     <div className="mx-auto max-w-5xl space-y-6 p-6">
       <div>
@@ -34,6 +54,8 @@ function TenderRadarContent() {
       <CoverageBanner />
       <FilterPanel />
       <ResultsList />
+
+      {tenderId && <TenderDetail tenderId={tenderId} onClose={closeDetail} />}
     </div>
   );
 }