feat(ci): add cachix publishing workflows

.tangled/workflows/publish-cachix-aarch64.yml

@@ -0,0 +1,20 @@
+when:
+  - event: ["push", "manual"]
+    branch: ["main"]
+
+engine: nixery
+
+dependencies:
+  nixpkgs:
+    - nix
+    - cachix
+    - gnugrep
+
+steps:
+  - name: Authenticate
+    command: |
+      cachix authtoken "$CACHIX_AUTH_TOKEN"
+
+  - name: Build and push aarch64
+    command: |
+      nix-store -qR --include-outputs $(nix-store -qd $(nix build .#packages.x86_64-linux.tranquil-pds-aarch64 --accept-flake-config --print-out-paths --no-link)) | grep -v '\.drv$' | cachix push "$CACHIX_CACHE_NAME"

.tangled/workflows/publish-cachix-x86_64.yml

@@ -0,0 +1,26 @@
+when:
+  - event: ["push", "manual"]
+    branch: ["main"]
+
+engine: nixery
+
+dependencies:
+  nixpkgs:
+    - nix
+    - cachix
+    - gnugrep
+
+steps:
+  - name: Authenticate
+    command: |
+      cachix authtoken "$CACHIX_AUTH_TOKEN"
+
+  - name: Build and push x86_64
+    command: |
+      nix-store -qR --include-outputs $(nix-store -qd $(nix build .#packages.x86_64-linux.tranquil-pds --accept-flake-config --print-out-paths --no-link)) | grep -v '\.drv$' | cachix push "$CACHIX_CACHE_NAME"
+      nix-store -qR --include-outputs $(nix-store -qd $(nix build .#packages.x86_64-linux.tranquil-frontend --accept-flake-config --print-out-paths --no-link)) | grep -v '\.drv$' | cachix push "$CACHIX_CACHE_NAME"
+
+  - name: Build and push devShell
+    command: |
+      nix develop --accept-flake-config --profile dev-profile -c true
+      cachix push "$CACHIX_CACHE_NAME" dev-profile

flake.nix

@@ -3,6 +3,21 @@
     nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
   };
 
+  nixConfig = {
+    extra-substituters = [
+      "https://tranquil.cachix.org"
+      "https://nix-community.cachix.org"
+      "https://cache.garnix.io"
+      "https://devenv.cachix.org"
+    ];
+    extra-trusted-public-keys = [
+      "tranquil.cachix.org-1:PoO+mGL6a6LcJiPakMDHN4E218/ei/7v2sxeDtNkSRg="
+      "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+      "cache.garnix.io:CTFPyKSLcx5RMJKfLo5EEPUObbA78b0YQ2DTCJXqr9g="
+      "devenv.cachix.org-1:w1cLUi8dv3hnoSPGAuibQv+f9TZLr6cv/Hm9XgU50cw="
+    ];
+  };
+
   outputs =
     {
       self,