UI: Restrict regex pattern for OAuth secrets

The current regex pattern will successfully match if the cache variable
contains the pattern anywhere inside the string. Let's restrict the
regex pattern such that it requires the pattern to be precisely between
the beginning and end of the string with no other characters in between
those anchor points.

UI/cmake/feature-restream.cmake

@@ -1,5 +1,5 @@
 if(RESTREAM_CLIENTID
-   AND RESTREAM_HASH MATCHES "(0|[a-fA-F0-9]+)"
+   AND RESTREAM_HASH MATCHES "^(0|[a-fA-F0-9]+)$"
    AND TARGET OBS::browser-panels)
   target_sources(obs-studio PRIVATE auth-restream.cpp auth-restream.hpp)
   target_enable_feature(obs-studio "Restream API connection" RESTREAM_ENABLED)

UI/cmake/feature-twitch.cmake

@@ -1,5 +1,5 @@
 if(TWITCH_CLIENTID
-   AND TWITCH_HASH MATCHES "(0|[a-fA-F0-9]+)"
+   AND TWITCH_HASH MATCHES "^(0|[a-fA-F0-9]+)$"
    AND TARGET OBS::browser-panels)
   target_sources(obs-studio PRIVATE auth-twitch.cpp auth-twitch.hpp)
   target_enable_feature(obs-studio "Twitch API connection" TWITCH_ENABLED)

UI/cmake/feature-youtube.cmake

@@ -1,7 +1,7 @@
 if(YOUTUBE_CLIENTID
    AND YOUTUBE_SECRET
-   AND YOUTUBE_CLIENTID_HASH MATCHES "(0|[a-fA-F0-9]+)"
-   AND YOUTUBE_SECRET_HASH MATCHES "(0|[a-fA-F0-9]+)")
+   AND YOUTUBE_CLIENTID_HASH MATCHES "^(0|[a-fA-F0-9]+)$"
+   AND YOUTUBE_SECRET_HASH MATCHES "^(0|[a-fA-F0-9]+)$")
   target_sources(
     obs-studio
     PRIVATE # cmake-format: sortable