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

flake.lock

@@ -90,6 +90,37 @@
         "type": "github"
       }
     },
+    "nixpkgs_3": {
+      "locked": {
+        "lastModified": 1786106723,
+        "narHash": "sha256-CgKDSHL6rqAAQkkvg1xaZDQXb77+4XW73iGcUMJ+2w0=",
+        "rev": "f13ff45afd1bb73e640eaa08a7066dbed07e3238",
+        "type": "tarball",
+        "url": "https://releases.nixos.org/nixos/unstable/nixos-26.11pre1049422.f13ff45afd1b/nixexprs.tar.zst"
+      },
+      "original": {
+        "type": "tarball",
+        "url": "https://channels.nixos.org/nixos-unstable/nixexprs.tar.zst"
+      }
+    },
+    "noctalia": {
+      "inputs": {
+        "nixpkgs": "nixpkgs_3"
+      },
+      "locked": {
+        "lastModified": 1786633340,
+        "narHash": "sha256-Kc3xbv2+z0+aV+t4IL1BfoTtB9MS0zHyI38oiv7zHxc=",
+        "owner": "noctalia-dev",
+        "repo": "noctalia-shell",
+        "rev": "4dd6f29dbaafde7b11d61ce12685d01441d4a483",
+        "type": "github"
+      },
+      "original": {
+        "owner": "noctalia-dev",
+        "repo": "noctalia-shell",
+        "type": "github"
+      }
+    },
     "plasma-manager": {
       "inputs": {
         "home-manager": [
@@ -118,6 +149,7 @@
         "claude-desktop": "claude-desktop",
         "home-manager": "home-manager",
         "nixpkgs": "nixpkgs_2",
+        "noctalia": "noctalia",
         "plasma-manager": "plasma-manager",
         "zen-browser": "zen-browser"
       }