frigate: write the config in one place

Only the detector and model section depends on the CPU check, but the
file was assembled in three heredocs writing to the same path. That
shape is what produced the safe-mode config: both branches used a plain
redirect and discarded everything above them.

Pick the variable part into DETECTOR_CONFIG first and write the file
once, so the layout is visible in one block and no branch can replace
what came before it.

Output is unchanged, verified by generating both branches from the
previous commit and from this one and diffing: byte-identical.

install/frigate-install.sh

@@ -269,6 +269,23 @@ GLOG_minloglevel=3
 GLOG_logtostderr=0
 EOF
 
+if grep -q -o -m1 -E 'avx[^ ]*|sse4_2' /proc/cpuinfo && [[ -f /openvino-model/ssdlite_mobilenet_v2.xml ]] && [[ -f /openvino-model/coco_91cl_bkgr.txt ]]; then
+  DETECTOR_CONFIG="detectors:
+  detector01:
+    type: openvino
+    device: AUTO
+model:
+  width: 300
+  height: 300
+  input_tensor: nhwc
+  input_pixel_format: bgr
+  path: /openvino-model/ssdlite_mobilenet_v2.xml
+  labelmap_path: /openvino-model/coco_91cl_bkgr.txt"
+else
+  DETECTOR_CONFIG="model:
+  path: /models/cpu_model.tflite"
+fi
+
 cat <<EOF >/config/config.yml
 mqtt:
   enabled: false
@@ -290,28 +307,8 @@ detect:
   enabled: false
 ffmpeg:
   hwaccel_args: auto
+${DETECTOR_CONFIG}
 EOF
-
-if grep -q -o -m1 -E 'avx[^ ]*|sse4_2' /proc/cpuinfo && [[ -f /openvino-model/ssdlite_mobilenet_v2.xml ]] && [[ -f /openvino-model/coco_91cl_bkgr.txt ]]; then
-  cat <<EOF >>/config/config.yml
-detectors:
-  detector01:
-    type: openvino
-    device: AUTO
-model:
-  width: 300
-  height: 300
-  input_tensor: nhwc
-  input_pixel_format: bgr
-  path: /openvino-model/ssdlite_mobilenet_v2.xml
-  labelmap_path: /openvino-model/coco_91cl_bkgr.txt
-EOF
-else
-  cat <<EOF >>/config/config.yml
-model:
-  path: /models/cpu_model.tflite
-EOF
-fi
 msg_ok "Configured Frigate"
 
 msg_info "Creating Services"