feat: break down core into explicit packages for Fedora remix compatibility

generic-release conflicts with fedora-release and generic-logos conflicts
with fedora-logos, so dishes shipping the remix packages cannot coexist
with @core pulling Fedora branding — the RPM transaction fails at prepare
time. Replace @core with the explicit core package list (mandatory +
default, plus basesystem/kernel/dhcp-client), add fedora-repos explicitly,
and deselect fedora-release/fedora-logos; the remix packages provide
system-release, system-release(44) and system-logos instead.

Verified on nuc6i7kyb: a Fedora 44 GNOME hypervisor desktop VM installed
cleanly from this configuration (982-package resolution scratch-tested
before the install).

cook/recipe_templates.yaml

@@ -23,7 +23,7 @@ base:
   - core/locale.ks
   - core/network.ks
   - core/services.ks
-  - packages/core.ks
+  - packages/core-explicit.ks
   - packages/fedora-remix.ks
   - packages/hand-picked.ks