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/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;