feat: implement profile system with mkHomeConfig and context constraints

- Add home/lib/default.nix with mkHomeConfig utility
  - Loads base + common modules always
  - Maps profiles (coding, gaming, media) to module imports
  - Enforces desktop/server mutual exclusion via assertion
  - Context must be 'desktop', 'server', or null

- Migrate all per-host home configs to new profile system
  - m3-ares: context=desktop, profiles=[coding, gaming, media]
  - m3-kratos: context=desktop, profiles=[coding, gaming, media]
  - m3-atlas: context=server, profiles=[coding]
  - m3-helios: context=server, profiles=[]
  - m3-hermes: context=server, profiles=[]
  - m3-aether: context=server, profiles=[]
  - m3-daedalus: context=desktop, profiles=[coding, media]

- Replace features.* options with new namespaces:
  - features.cli.* -> base.shell.* / base.cliTools.* / base.secrets
  - features.desktop.* -> desktop.wm.* / desktop.apps.* / desktop.theme.*
  - gaming/media moved to profiles.gaming.* / profiles.media.*

- Fix home/coding/editor/neovim.nix: remove duplicate option declaration
  (coding.editors.neovim.enable already declared by m3ta-nixpkgs)

- Fix home/coding/lsp/servers.nix: replace removed nodePackages.typescript-language-server
  with typescript-language-server

- Fix home/desktop/theme/wallpapers.nix: correct relative path
  (was ../../.. which resolved to project root, should be ../..)

home/m3tam3re/m3-helios.nix

@@ -1,17 +1,33 @@
+# m3-helios — AdGuard DNS and internal routing server.
+# Context: server | Profiles: (none)
 {
+  lib,
+  ...
+}:
+let
+  homeLib = import ../lib { inherit lib; };
+in {
   imports = [
-    ../common
-    ../features/cli
+    (homeLib.mkHomeConfig {
+      profiles = [ ];
+      context = "server";
+    })
     ./home-server.nix
+    # Fish shell — no equivalent in new base module yet
+    ../features/cli/fish.nix
   ];
 
-  features = {
-    cli = {
-      fish.enable = true;
-      fzf.enable = true;
-      nitch.enable = true;
-      secrets.enable = false;
+  # Base CLI tools (new namespace)
+  base = {
+    shell = {
       starship.enable = true;
     };
+    cliTools = {
+      fzf.enable = true;
+      nitch.enable = true;
+    };
   };
+
+  # Fish shell (legacy — no new equivalent yet)
+  features.cli.fish.enable = true;
 }