Initial cluster config: NixOS flake + k3s + 5 node definitions

- Multi-host flake.nix (3x N97 x86_64 + 2x RPi4 aarch64)
- Shared modules: k3s-cluster, tailscale, meos-gateway
- Node configs: n97-1 (control plane), n97-2/n97-3 (Ollama workers), rpi4-1/rpi4-2 (ARM workers)
- K8s manifests: Forgejo, Postgres (CNPG), Umami, OpenBrain, MeOS Dashboard, MCP servers
- Bootstrap and DB migration scripts
- Migration plan doc (7-day phased rollout)

flake.nix

@@ -0,0 +1,48 @@
+{
+  description = "Scobleclaw Multi-Node Cluster — NixOS + k3s";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-25.11";
+  };
+
+  outputs = { self, nixpkgs }:
+    let
+      shared-modules = [
+        ./modules/tailscale.nix
+        ./modules/k3s-cluster.nix
+      ];
+
+      mkSystem = system: hostModule: nixpkgs.lib.nixosSystem {
+        inherit system;
+        modules = shared-modules ++ [ hostModule ];
+        specialArgs = { inherit self; };
+      };
+    in {
+      nixosConfigurations = {
+        n97-1 = mkSystem "x86_64-linux" [
+          ./hardware-n97.nix
+          ./nodes/n97-1.nix
+        ];
+
+        n97-2 = mkSystem "x86_64-linux" [
+          ./hardware-n97.nix
+          ./nodes/n97-2.nix
+        ];
+
+        n97-3 = mkSystem "x86_64-linux" [
+          ./hardware-n97.nix
+          ./nodes/n97-3.nix
+        ];
+
+        rpi4-1 = mkSystem "aarch64-linux" [
+          ./hardware-rpi4.nix
+          ./nodes/rpi4-1.nix
+        ];
+
+        rpi4-2 = mkSystem "aarch64-linux" [
+          ./hardware-rpi4.nix
+          ./nodes/rpi4-2.nix
+        ];
+      };
+    };
+}