feat: integrate m3ta-home for centralized user profiles

- Add m3ta-home as flake input (ssh://gitea@code.m3ta.dev/m3tam3re/m3ta-home)
- Rewrite hosts/common/users/m3tam3re.nix to use m3ta-home.lib.mkHome
- Central host profile mapping (context + sets per hostname)
- Per-host feature flags for desktop vs server hosts
- Extract Hyprland monitor layouts to hosts/<name>/home.nix
- Per-host home.nix auto-imported if file exists

BREAKING: This replaces the old home/m3tam3re/<host>.nix system.
The old home/ directory is kept but no longer referenced.
It should be removed in a follow-up commit after verification.

hosts/m3-kratos/home.nix

@@ -0,0 +1,34 @@
+# hosts/m3-kratos/home.nix — Host-specific home-manager overrides.
+# AMD desktop: dual 1440p monitors.
+{config, lib, ...}:
+with lib; {
+  # ── Hyprland monitor layout ──
+  config = mkIf config.desktop.wm.hyprland.enable {
+    wayland.windowManager.hyprland = {
+      enable = true;
+      settings = {
+        monitor = [
+          "DP-1,2560x1440@144,0x0,1"
+          "DP-2,2560x1440@144,2560x0,1"
+        ];
+        workspace = [
+          "1, monitor:DP-1, default:true"
+          "2, monitor:DP-1"
+          "3, monitor:DP-1"
+          "4, monitor:DP-2"
+          "5, monitor:DP-2"
+          "6, monitor:DP-2"
+          "7, monitor:DP-2"
+        ];
+        windowrule = [
+          "match:class dev.zed.Zed, workspace 1"
+          "match:class Msty, workspace 1"
+          "match:class ^(com.obsproject.Studio)$, workspace 2"
+          "match:class ^(brave-browser)$, workspace 4, opacity 1.0"
+          "match:class ^(vivaldi-stable)$, workspace 4, opacity 1.0"
+          "match:class ^steam_app_\\d+$, idle_inhibit focus"
+        ];
+      };
+    };
+  };
+}