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

packages/betacode.nix

@@ -0,0 +1,16 @@
+{
+  writers,
+  haskell,
+  haskellPackages,
+}:
+writers.writeHaskellBin "betacode" {
+  libraries = [
+    (haskell.lib.unmarkBroken (haskell.lib.doJailbreak haskellPackages.betacode))
+    haskellPackages.text
+  ];
+} ''
+  import qualified Data.Text.IO as T
+  import qualified Data.Text as T
+  import Text.BetaCode
+  main = T.interact (either (error . T.unpack) id . fromBeta)
+''