feat(firefox): finalize web-app profile with solid autohide and tridactyl integration

- Unified autohide for Tabs and Nav-bar with solid background.

- Implemented dynamic newtab via TRIDACTYL_NEWTAB env var.

- Cleaned up redundant new-tab-override extension.

apps/firefox/profiles/web-app.nix

@@ -14,14 +14,9 @@
     ublock-origin
     bitwarden
     tridactyl
-    new-tab-override
   ];
 
   settings = {
-    # --- New Tab Override ---
-    "extensions.newtaboverride@agenedia.com.url" = url;
-    "extensions.newtaboverride@agenedia.com.type" = 1; # URL mode
-
     # --- Privacy & Hardening ---
     "browser.contentblocking.category" = "strict";
     "privacy.trackingprotection.enabled" = true;
@@ -99,6 +94,7 @@
       transition:  transform var(--uc-autohide-toolbar-duration) ease var(--uc-autohide-toolbar-delay), opacity var(--uc-autohide-toolbar-duration) ease var(--uc-autohide-toolbar-delay) !important;
       position: relative;
       z-index: 2;
+      background-color: #1c1b22 !important; /* Solid background */
     }
 
     #navigator-toolbox,