feat: replace loupe with imv and update plymouth theme

- Replaced Loupe with imv for a keyboard-driven image viewer experience.

- Updated Plymouth logo with Firewatch-inspired ASCII art gradient.

- Updated Plymouth background color to match Firewatch palette (#2D112A).

apps/imv/default.nix

@@ -0,0 +1,23 @@
+{pkgs, ...}: {
+  home.packages = with pkgs; [imv];
+
+  xdg.mimeApps = {
+    enable = true;
+    defaultApplications = {
+      "image/png" = "imv.desktop";
+      "image/jpeg" = "imv.desktop";
+      "image/gif" = "imv.desktop";
+      "image/webp" = "imv.desktop";
+      "image/bmp" = "imv.desktop";
+      "image/svg+xml" = "imv.desktop";
+      "image/tiff" = "imv.desktop";
+    };
+  };
+
+  wayland.windowManager.hyprland.settings.windowrulev2 = [
+    # --- IMAGE VIEWER (IMV) ---
+    "float, class:^(imv)$"
+    "center, class:^(imv)$"
+    "size 70% 70%, class:^(imv)$"
+  ];
+}