chore: replace uint8-to-base64 with native btoa/atob (#38579)

Replace the single-use `uint8-to-base64` dependency with native
`btoa`/`atob`. The implementation is exactly identical.

---------

Signed-off-by: silverwind <me@silverwind.io>

pnpm-lock.yaml

@@ -185,9 +185,6 @@ importers:
       tributejs:
         specifier: 5.1.3
         version: 5.1.3
-      uint8-to-base64:
-        specifier: 0.2.1
-        version: 0.2.1
       vanilla-colorful:
         specifier: 0.7.2
         version: 0.7.2
@@ -4183,9 +4180,6 @@ packages:
   uc.micro@2.1.0:
     resolution: {integrity: sha512-ARDJmphmdvUk6Glw7y9DQ2bFkKBHwQHLi2lsaH6PPmz/Ka9sFOBsBluozhDltWmnv9u/cF6Rt87znRTPV+yp/A==}
 
-  uint8-to-base64@0.2.1:
-    resolution: {integrity: sha512-uO/84GaoDUfiAxpa8EksjVLE77A9Kc7ZTziN4zRpq4de9yLaLcZn3jx1/sVjyupsywcVX6RKWbqLe7gUNyzH+Q==}
-
   unbox-primitive@1.1.0:
     resolution: {integrity: sha512-nWJ91DjeOkej/TA8pXQ3myruKpKEYgqvpw9lz4OPHj/NWFNluYrjbz9j01CJ8yKQd2g4jFoOkINCTW2I5LEEyw==}
     engines: {node: '>= 0.4'}
@@ -8902,8 +8896,6 @@ snapshots:
 
   uc.micro@2.1.0: {}
 
-  uint8-to-base64@0.2.1: {}
-
   unbox-primitive@1.1.0:
     dependencies:
       call-bound: 1.0.4