feat: create new home/ directory structure for profile-based config

New structure:
- home/base/        - Always loaded (shell, cli-tools, secrets)
- home/coding/      - Profile-independent dev tooling (editor, lsp, git, agents)
- home/profiles/    - Freely combinable profiles (gaming, media)
- home/desktop/     - Desktop-only (wm, apps, theme)
- home/server/      - Minimal server stub

Migration sources:
- home/features/cli/ → home/base/{shell,cli-tools,secrets}
- home/features/desktop/hyprland,wayland,rofi → home/desktop/wm/
- home/features/desktop/obsidian,office,webapps,crypto → home/desktop/apps/
- home/features/desktop/fonts,theme,wallpapers → home/desktop/theme/
- gaming.nix split → home/profiles/gaming/{steam,gamescope}
- media.nix split  → home/profiles/media/{obs,ffmpeg,yt-dlp,kdenlive,handbrake}

Option namespaces updated:
- features.cli.*  → base.shell.* / base.cliTools.* / base.secrets
- features.desktop.* → desktop.wm.* / desktop.apps.* / desktop.theme.*
- features.desktop.gaming → profiles.gaming.*
- features.desktop.media  → profiles.media.*

Verified: nix flake check passes (warnings only)

home/profiles/gaming/default.nix

@@ -0,0 +1,7 @@
+# Gaming profile aggregator — Steam platform and Gamescope session support.
+{...}: {
+  imports = [
+    ./steam.nix
+    ./gamescope.nix
+  ];
+}

home/profiles/gaming/gamescope.nix

@@ -0,0 +1,16 @@
+# Gamescope — Valve's micro-compositor for Steam gaming sessions.
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+with lib; let
+  cfg = config.profiles.gaming.gamescope;
+in {
+  options.profiles.gaming.gamescope.enable = mkEnableOption "enable Gamescope session";
+
+  config = mkIf cfg.enable {
+    home.packages = [pkgs.gamescope];
+  };
+}

home/profiles/gaming/steam.nix

@@ -0,0 +1,21 @@
+# Steam gaming platform with Steam Deck compatibility tools and gaming utilities.
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+with lib; let
+  cfg = config.profiles.gaming.steam;
+in {
+  options.profiles.gaming.steam.enable = mkEnableOption "enable Steam gaming";
+
+  config = mkIf cfg.enable {
+    home.packages = with pkgs; [
+      gamemode
+      goverlay
+      mangohud
+      protonplus
+    ];
+  };
+}