Add SD image pipeline, documentation overhaul, and fix module issues

- Add automatic SD image builds for Raspberry Pi via Forgejo Actions
- Enable binfmt emulation on cryodev-main for aarch64 cross-builds
- Add sd-image.nix module to cryodev-pi configuration
- Create comprehensive docs/ structure with installation guides
- Split installation docs into: first-install (server), reinstall, new-client (Pi)
- Add lib/utils.nix and apps/rebuild from synix
- Fix headplane module for new upstream API (tale/headplane)
- Fix various module issues (mailserver stateVersion, option conflicts)
- Add placeholder secrets.yaml files for both hosts
- Remove old INSTRUCTIONS.md (content moved to docs/)

modules/nixos/sops/default.nix

@@ -7,7 +7,16 @@
 }:
 
 let
-  secrets = "${toString inputs.self}/hosts/${config.networking.hostName}/secrets/secrets.yaml";
+  # Check both locations for secrets.yaml
+  secretsInSubdir = "${toString inputs.self}/hosts/${config.networking.hostName}/secrets/secrets.yaml";
+  secretsInRoot = "${toString inputs.self}/hosts/${config.networking.hostName}/secrets.yaml";
+  secrets =
+    if builtins.pathExists secretsInSubdir then
+      secretsInSubdir
+    else if builtins.pathExists secretsInRoot then
+      secretsInRoot
+    else
+      null;
 in
 {
   imports = [ inputs.sops-nix.nixosModules.sops ];
@@ -17,5 +26,5 @@ in
     sops
   ];
 
-  sops.defaultSopsFile = lib.mkIf (builtins.pathExists secrets) (lib.mkDefault secrets);
+  sops.defaultSopsFile = lib.mkIf (secrets != null) (lib.mkDefault secrets);
 }