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/.gitignore

@@ -0,0 +1,29 @@
+# Ignore the following files
+*~
+*.[oa]
+*.diff
+*.kate-swp
+*.kdev4
+.kdev_include_paths
+*.kdevelop.pcs
+*.moc
+*.moc.cpp
+*.orig
+*.user
+.*.swp
+.swp.*
+Doxyfile
+Makefile
+avail
+random_seed
+/build*/
+CMakeLists.txt.user*
+*.unc-backup*
+.cmake/
+/.clang-format
+/compile_commands.json
+.clangd
+.idea
+.vscode
+/cmake-build*
+.cache