fix: KF6Attica recipe, kf6-knewstuff Attica dep, topo-sort cycle error

- Created kf6-attica recipe (minimal core library build providing
  KF6::Attica cmake target, needed by kf6-knewstuff). v6.10.0,
  QML/tests/examples disabled.
- Added kf6-attica to redbear-full.toml config, integrate-redbear.sh
  symlink, and recipes/kde/ symlink.
- Fixed kf6-knewstuff: removed stale find_package(KF6Attica)
  suppression; added kf6-attica as dependency. Now publishes
  to repo (core-only build produces empty package — upstream
  code structure yields no libs with QtQuick/widgets/tools off).
- Cookbook topo-sort: changed cycle fallback from silent
  Ok(recipes) to Err(Recursion) — surfaces dependency graph
  bugs instead of hiding them.
- Fixed stale QtNetwork comment: QtNetwork IS enabled in qtbase
  since 2026-04-29 (relibc DNS resolver hardened).
- Verified: kf6-attica builds, kf6-knewstuff publishes to repo

local/recipes/kde/kf6-attica/source/metainfo.yaml

@@ -0,0 +1,21 @@
+maintainer:
+description: Open Collaboration Services API
+tier: 1
+type: functional
+platforms:
+    - name: Linux
+    - name: FreeBSD
+    - name: Windows
+    - name: macOS
+    - name: Android
+portingAid: false
+deprecated: false
+release: true
+libraries:
+ - cmake: "KF6::Attica"
+   license: LGPL-2.1-only OR LGPL-3.0-only
+cmakename: KF6Attica
+
+public_lib: true
+group: Frameworks
+subgroup: Tier 1