feat: overhaul config — noctalia shell, niri keybinds, battery, extra packages

- niri: switch from replaceStrings patching to plain config.kdl for simplicity
- niri: add Mod+Shift+Q (close), Mod+Shift+HJKL/Arrow (move window),
  Mod+Shift+1-9 (move to workspace)
- niri: add layer-rule to disable background-blur on noctalia bar (fix seam)
- noctalia: add capsule_group for cpu+ram (group:sysmon), panel_overlap,
  contact_shadow; corner_radius_scale 1.0
- noctalia: add all LC_* locale overrides in plasma-localerc (fix vi_VN calendar)
- system: TLP (battery), UPower, disable power-profiles-daemon (conflicts with TLP)
- system: DDC/CI support (ddcutil + i2c-dev + hardware.i2c)
- system: enable fish shell system-wide
- packages: add tree, fish, ddcutil; noctalia required services documented
- README: full rewrite with current structure, keybinds, fresh-install steps

home/modules/applications/default.nix

@@ -47,6 +47,7 @@
     wl-clipboard
 
     # CLI tools
+    tree
     vim
     neovim
     tmux
@@ -70,12 +71,13 @@
     # System control
     brightnessctl
     playerctl
+    ddcutil
 
     # Dev tools
     gh
   ];
 
-  # KDE Plasma session: dark theme + touchpad preferences
+  # KDE Plasma session: dark theme + touchpad preferences + English locale
   programs.plasma = {
     enable = true;
     workspace.lookAndFeel = "org.kde.breezedark.desktop";
@@ -89,5 +91,19 @@
         scrollSpeed   = 0.75;
       }
     ];
+    # Force all KDE format/calendar locale to English so the clock widget,
+    # calendar, and date/number formatting don't fall back to vi_VN.
+    configFile."plasma-localerc"."Formats" = {
+      LANG           = "en_US.UTF-8";
+      LC_TIME        = "en_US.UTF-8";
+      LC_NUMERIC     = "en_US.UTF-8";
+      LC_MONETARY    = "en_US.UTF-8";
+      LC_MEASUREMENT = "en_US.UTF-8";
+      LC_COLLATE     = "en_US.UTF-8";
+      LC_ADDRESS     = "en_US.UTF-8";
+      LC_NAME        = "en_US.UTF-8";
+      LC_TELEPHONE   = "en_US.UTF-8";
+      LC_PAPER       = "en_US.UTF-8";
+    };
   };
 }