feat: Mehrsprachigkeit EN/FR/ES via Mistral + Sprachumschalter

- Übersetzung per ministral-3b-latest (on-demand + DB-Cache)
- Sprachumschalter im Detailseiten-Header (DE/EN/FR/ES)
- ?lang= Query-Parameter auf /beitrag/<id>
- Neue translations-Tabelle mit submission_id+lang UNIQUE

src/app.py

@@ -3323,7 +3323,7 @@ def public_frontend():
   </div>
 </div>
 
-<header class="site-header">
+<button id="navToggle" class="nav-toggle" aria-label="Menü öffnen">☰</button>
   <button id="navToggle" class="nav-toggle" aria-label="Menü öffnen">☰</button>
   <a href="/" class="site-logo">
     <img src="/static/logo.png" alt="Brettspiel News" style="height:38px;width:auto;display:block;">
@@ -4180,6 +4180,72 @@ def api_query():
 
 
 
+
+# ── Übersetzung via Mistral ──
+LANG_NAMES = {"en": "Englisch", "fr": "Französisch", "es": "Spanisch"}
+LANG_FLAGS = {"en": "🇬🇧", "fr": "🇫🇷", "es": "🇪🇸"}
+
+def translate_text(text: str, target_lang: str, content_type: str = "Beitrag") -> str:
+    """Übersetzt text via Mistral API in target_lang (en/fr/es)."""
+    if not text or not text.strip():
+        return text
+    api_key = os.environ.get("MISTRAL_API_KEY", "")
+    if not api_key:
+        return text  # fallback: Originaltext
+
+    lang_name = LANG_NAMES.get(target_lang, target_lang)
+    prompt = (
+        f"Übersetze folgenden {content_type} ins {lang_name}. "
+        f"Nur die Übersetzung zurückgeben, keine Erklärungen. "
+        f"Behalte Zeilenumbrüche und Absätze bei:\n\n{text}"
+    )
+    try:
+        r = requests.post(
+            "https://api.mistral.ai/v1/chat/completions",
+            headers={"Authorization": f"Bearer {api_key}", "Content-Type": "application/json"},
+            json={"model": "ministral-3b-latest", "messages": [
+                {"role": "user", "content": prompt}
+            ], "max_tokens": 2000, "temperature": 0.2},
+            timeout=30,
+        )
+        if r.status_code == 200:
+            translated = r.json()["choices"][0]["message"]["content"].strip()
+            return translated
+    except Exception:
+        pass
+    return text  # fallback bei Fehler
+
+def get_translated_content(db, sub_id: int, target_lang: str, row) -> dict:
+    """Holt Übersetzung aus Cache oder übersetzt via Mistral."""
+    if target_lang == "de":
+        return {"content": (row["summary"] or row["content"] or "").strip(),
+                "display_text": row["display_text"] or ""}
+
+    cached = db.execute(
+        "SELECT content, display_text FROM translations WHERE submission_id=? AND lang=?",
+        (sub_id, target_lang)
+    ).fetchone()
+
+    if cached:
+        return {"content": cached["content"] or "", "display_text": cached["display_text"] or ""}
+
+    original_content = (row["summary"] or row["content"] or "").strip()
+    original_display = row["display_text"] or ""
+
+    translated_content = translate_text(original_content, target_lang, "Beitrag")
+    translated_display = translate_text(original_display, target_lang, "Anzeigetext") if original_display else ""
+
+    try:
+        db.execute(
+            "INSERT OR REPLACE INTO translations (submission_id, lang, content, display_text) VALUES (?,?,?,?)",
+            (sub_id, target_lang, translated_content, translated_display)
+        )
+        db.commit()
+    except Exception:
+        pass
+
+    return {"content": translated_content, "display_text": translated_display}
+
 @app.route('/api/chat', methods=['POST'])
 def api_chat():
     """Chat agent with read-only access to published submissions."""
@@ -4637,6 +4703,9 @@ def api_submit():
 
 @app.route("/beitrag/<int:sub_id>")
 def public_detail(sub_id: int):
+    lang = request.args.get("lang", "de")
+    if lang not in ("de", "en", "fr", "es"):
+        lang = "de"
     """Public detail view — full media, text, and metadata."""
     import base64
     db = get_db()
@@ -4709,7 +4778,10 @@ def public_detail(sub_id: int):
     except Exception:
         pass
 
-    content = (row["summary"] or row["content"] or "").strip()
+    # ── Mehrsprachigkeit: Übersetzung laden/cachen ──
+    translation = get_translated_content(db, sub_id, lang, row)
+    content = translation["content"]
+    display_text = translation["display_text"]
 
     # Comments
     comment_rows = db.execute(
@@ -4835,11 +4907,26 @@ def public_detail(sub_id: int):
   .detail-like-btn:hover {{ opacity:0.8; }}
   .detail-like-btn.liked {{ background:none; }}
   .detail-like-btn.liked svg, .detail-like-btn.liked svg path {{ stroke:#EF4444 !important; fill:#EF4444 !important; }}
-  .detail-like-btn:active {{ transform:scale(0.94); }}</style>
+  .detail-like-btn:active {{ transform:scale(0.94); }}
+  .lang-switcher {{ display:flex; gap:0.3rem; margin-right:auto; }}
+  .lang-btn {{ text-decoration:none; font-size:1rem; padding:0.2rem 0.35rem; border-radius:6px; transition:all 0.15s; opacity:0.5; line-height:1; }}
+  .lang-btn:hover {{ opacity:0.8; background:rgba(255,255,255,0.1); }}
+  .lang-btn.active {{ opacity:1; background:rgba(32,34,138,0.3); }}
+  @media(max-width:600px) {{
+    .lang-switcher {{ gap:0.15rem; }}
+    .lang-btn {{ font-size:0.85rem; padding:0.15rem 0.25rem; }}
+  }}
+</style>
 <link rel="stylesheet" href="/static/theme.css">
 </head>
 <body>
 <header class="site-header">
+  <div class="lang-switcher">
+    <a href="?lang=de" class="lang-btn {'active' if lang == 'de' else ''}">🇩🇪</a>
+    <a href="?lang=en" class="lang-btn {'active' if lang == 'en' else ''}">🇬🇧</a>
+    <a href="?lang=fr" class="lang-btn {'active' if lang == 'fr' else ''}">🇫🇷</a>
+    <a href="?lang=es" class="lang-btn {'active' if lang == 'es' else ''}">🇪🇸</a>
+  </div>
   <button id="navToggle" class="nav-toggle" aria-label="Menü öffnen">☰</button>
   <a href="/" class="site-logo">
     <img src="/static/logo.png" alt="Brettspiel News" style="height:38px;width:auto;display:block;" width="160" height="30">