Fix OpenAI array content, add error logging, Ollama reachability warning

- Normalize OpenAI array-format content to string to fix connection reset
- Add error.log with rotating handler for proxy and stream errors
- Add global unhandled exception handler returning JSON 500
- Write OLLAMA_URL/DEFAULT_MODEL env vars to DB on startup (reset on restart)
- Add extra_hosts to docker-compose.yml for host.docker.internal on Linux
- Show warning in admin UI when Ollama URL is unreachable
- Return reachable: true/false from /api/ollama-models endpoint

frontend/src/main.jsx

@@ -80,6 +80,7 @@ function SettingsSection({ password }) {
   const [settings, setSettings] = useState(null);
   const [availableModels, setAvailableModels] = useState([]);
   const [modelsLoading, setModelsLoading] = useState(false);
+  const [ollamaReachable, setOllamaReachable] = useState(true);
   const [proxyEndpoint, setProxyEndpoint] = useState(null);
   const [saved, setSaved] = useState(false);
   const [error, setError] = useState(null);
@@ -91,12 +92,14 @@ function SettingsSection({ password }) {
         headers: authHeaders(password),
         params: url ? { url } : {},
       });
-      const models = res.data.models;
+      const { models, reachable } = res.data;
+      setOllamaReachable(reachable);
       setAvailableModels(models);
       if (models.length > 0 && !models.includes(currentModel)) {
         setSettings(s => ({ ...s, default_model: models[0] }));
       }
     } catch {
+      setOllamaReachable(false);
       setAvailableModels([]);
     } finally {
       setModelsLoading(false);
@@ -144,14 +147,19 @@ function SettingsSection({ password }) {
         </div>
         <div className="settings-row">
           <label>Ollama-Endpunkt</label>
-          <input
-            type="url"
-            value={settings.ollama_url}
-            onChange={(e) => setSettings({ ...settings, ollama_url: e.target.value })}
-            onBlur={(e) => fetchModels(e.target.value, settings.default_model)}
-            placeholder="http://localhost:11434"
-            required
-          />
+          <div className="settings-input-wrap">
+            <input
+              type="url"
+              value={settings.ollama_url}
+              onChange={(e) => setSettings({ ...settings, ollama_url: e.target.value })}
+              onBlur={(e) => fetchModels(e.target.value, settings.default_model)}
+              placeholder="http://localhost:11434"
+              required
+            />
+            {!ollamaReachable && !modelsLoading && (
+              <div className="warning">⚠ Ollama nicht erreichbar unter {settings.ollama_url}</div>
+            )}
+          </div>
         </div>
         <div className="settings-row">
           <label>Standard-Modell</label>

frontend/src/styles.css

@@ -194,6 +194,31 @@ tr:hover {
   font-size: 14px;
 }
 
+.settings-input-wrap {
+  flex: 1;
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+}
+
+.settings-input-wrap input {
+  width: 100%;
+  padding: 8px 10px;
+  border: 1px solid #ccc;
+  border-radius: 4px;
+  font-size: 14px;
+  box-sizing: border-box;
+}
+
+.warning {
+  color: #b8520a;
+  background: #fff3e0;
+  border: 1px solid #e67e22;
+  border-radius: 4px;
+  padding: 6px 10px;
+  font-size: 13px;
+}
+
 .settings-form button {
   align-self: flex-start;
   padding: 8px 20px;