feat: initial m3ta-home structure

- flake.nix with nixpkgs, home-manager, nix-colors, m3ta-nixpkgs, agenix, NUR inputs
- lib/mkHome.nix: compose HM config from user + identity + context + sets
- profiles/base: shell, cli-tools, secrets (always loaded)
- profiles/contexts/desktop: WM, apps, theme, ghostty
- profiles/contexts/server: minimal headless
- profiles/sets/coding: core (git, direnv, jq, rg), editor, lsp, languages, agents
- profiles/sets/gaming: steam, gamescope, gpu
- profiles/sets/media: obs, ffmpeg, kdenlive, handbrake, yt-dlp
- users/m3tam3re/identities: private.nix, work.nix (git, jj, ssh per identity)
- users/m3tam3re/preferences: cliphist, difftastic, base packages

profiles/contexts/desktop/theme/theme.nix

@@ -0,0 +1,24 @@
+# GTK and Qt theming — Dracula theme with matching icons and cursor.
+{
+  pkgs,
+  config,
+  ...
+}: {
+  qt = {
+    enable = true;
+    platformTheme.name = "gtk";
+  };
+
+  gtk = {
+    enable = true;
+    theme = {
+      name = "Dracula";
+      package = pkgs.dracula-theme;
+    };
+    iconTheme = {
+      name = "Dracula";
+      package = pkgs.dracula-icon-theme;
+    };
+    gtk4.theme = config.gtk.theme;
+  };
+}