Miscellaneous fixes (#23082)

* openvino log message and preview directory checks

* restrict config vars for viewer users

* recording timestamp fix

when startTime is exactly on an hour boundary, findIndex returns the first matching chunk, which is the previous hour's chunk (where before == startTime), instead of the correct chunk (where after == startTime)

the bug shows up when using the share timestamp feature and sharing a specific timestamp on the exact hour mark. when accessing the shared link, the timeline would jump to the incorrect hour

* use helper for chunked time range

* Adjustments to contributing docs

* tweak

* Improve wording

* tweak

---------

Co-authored-by: Nicolas Mowen <nickmowen213@gmail.com>

frigate/api/app.py

@@ -146,8 +146,13 @@ def config(request: Request):
         for name, detector in config_obj.detectors.items()
     }
 
-    # remove the mqtt password
+    # remove environment_vars for non-admin users
+    if request.headers.get("remote-role") != "admin":
+        config.pop("environment_vars", None)
+
+    # remove mqtt credentials
     config["mqtt"].pop("password", None)
+    config["mqtt"].pop("user", None)
 
     # remove the proxy secret
     config["proxy"].pop("auth_secret", None)