Fix nix flake check warnings and errors

- Move nextcloud-talk-desktop to x86_64-linux-only block (fixes aarch64 eval error)
- Remove duplicate deps from plasma-bigscreen (auto-injected by mkKdeDerivation)
- Replace nixfmt-rfc-style with nixfmt (deprecated alias)
- Set programs.git.signing.format = null (adopt new default)
- Add meta.description to all flake apps

roles/plasma-bigscreen/package.nix

@@ -62,33 +62,22 @@ mkKdeDerivation {
   ];
 
   extraBuildInputs = [
-    # KDE Frameworks
-    ki18n
+    # KDE Frameworks (auto-injected by mkKdeDerivation: ki18n, kcmutils,
+    # knotifications, kio, kwayland, kwindowsystem, ksvg, kiconthemes)
     kdeclarative
-    kcmutils
-    knotifications
-    kio
-    kwayland
-    kwindowsystem
-    ksvg
-    kiconthemes
     kglobalaccel
     kdbusaddons
-    # Plasma
-    plasma-workspace
+    # Plasma (auto-injected: plasma-workspace, plasma-activities,
+    # plasma-activities-stats, libkscreen)
     plasma-nano
     plasma-nm
-    plasma-activities
-    plasma-activities-stats
     milou
-    libkscreen
     kdeconnect-kde
     # Qt — qtdeclarative is needed for Qt6::QmlPrivate (see postPatch)
     qtdeclarative
     qtmultimedia
     qtwebengine
-    # Other
-    bluez-qt
+    # Other (auto-injected: bluez-qt)
     qcoro
     plasma-wayland-protocols
     wayland
@@ -96,22 +85,22 @@ mkKdeDerivation {
   ];
 
   postPatch = ''
-    substituteInPlace bin/plasma-bigscreen-wayland.in \
-      --replace @KDE_INSTALL_FULL_LIBEXECDIR@ "${plasma-workspace}/libexec"
+        substituteInPlace bin/plasma-bigscreen-wayland.in \
+          --replace @KDE_INSTALL_FULL_LIBEXECDIR@ "${plasma-workspace}/libexec"
 
-    # WORKAROUND: Plasma version numbers must match; we're building an
-    # unreleased package against a stable Plasma release. Remove once
-    # bigscreen is part of the Plasma release cycle.
-    substituteInPlace CMakeLists.txt \
-      --replace-fail 'set(PROJECT_VERSION "6.5.80")' 'set(PROJECT_VERSION "${plasma-workspace.version}")'
+        # WORKAROUND: Plasma version numbers must match; we're building an
+        # unreleased package against a stable Plasma release. Remove once
+        # bigscreen is part of the Plasma release cycle.
+        substituteInPlace CMakeLists.txt \
+          --replace-fail 'set(PROJECT_VERSION "6.5.80")' 'set(PROJECT_VERSION "${plasma-workspace.version}")'
 
-    # WORKAROUND: QCoro6Qml's cmake config links against Qt6::QmlPrivate but
-    # doesn't call find_package to import the target. This is arguably a QCoro
-    # packaging bug in nixpkgs (it should propagate qtdeclarative). Remove
-    # once QCoro or the nixpkgs plasma-bigscreen package is fixed upstream.
-    substituteInPlace CMakeLists.txt \
-      --replace-fail 'find_package(QCoro6' 'find_package(Qt6 ''${QT_MIN_VERSION} CONFIG REQUIRED COMPONENTS QmlPrivate)
-find_package(QCoro6'
+        # WORKAROUND: QCoro6Qml's cmake config links against Qt6::QmlPrivate but
+        # doesn't call find_package to import the target. This is arguably a QCoro
+        # packaging bug in nixpkgs (it should propagate qtdeclarative). Remove
+        # once QCoro or the nixpkgs plasma-bigscreen package is fixed upstream.
+        substituteInPlace CMakeLists.txt \
+          --replace-fail 'find_package(QCoro6' 'find_package(Qt6 ''${QT_MIN_VERSION} CONFIG REQUIRED COMPONENTS QmlPrivate)
+    find_package(QCoro6'
   '';
 
   preFixup = ''