feat: fix secrets permissions, move ./packages to flake outputs

packages/mpv-radio.nix

@@ -0,0 +1,29 @@
+{
+  writeText,
+  lib,
+  writers,
+  mpv,
+  dmenu,
+  coreutils,
+  gnused,
+  di-fm-key-file,
+}: let
+  streams = import ../lib/streams.nix {
+    di-fm-key = "%DI_FM_KEY%";
+  };
+  streams-tsv = writeText "streams.tsv" (lib.concatMapStringsSep "\n" ({
+    desc ? "",
+    stream,
+    station,
+    ...
+  }: "${station}\t${desc}\t${stream}")
+  streams);
+in
+  writers.writeDashBin "mpv-radio" ''
+    export DI_FM_KEY=$(cat "${di-fm-key-file}")
+    exec ${mpv}/bin/mpv --force-window=yes "$(
+      ${dmenu}/bin/dmenu -i -l 5 < ${streams-tsv} \
+        | ${coreutils}/bin/cut -f3 \
+        | ${gnused}/bin/sed s/%DI_FM_KEY%/"$DI_FM_KEY"/
+    )"
+  ''