Update repository URLs to HamRadioOnline organisation (#142)

* Move remaining references to the HamRadioOnline organisation

The repository moved from praktimarc/kst4contest to
HamRadioOnline/kst4contest. Document the move in the German and English
changelog, point manuals, README, website, AUR packaging and the
version-feed tooling at the new address, and keep accepting pre-move
release URLs in the update-feed validator because published feeds still
carry the old owner. Personal identities (Ko-Fi account, contact
e-mail) stay unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WFGQ7wkSPo21itLMHPi8Yw

* Lowercase the owner in the generated Flatpak Pages URL

GITHUB_REPOSITORY_OWNER is now the mixed-case HamRadioOnline, and the
next build would write that spelling into the published flatpakrepo and
flatpakref files. Hostnames are case-insensitive, but the published
metadata should match the documented lowercase address.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WFGQ7wkSPo21itLMHPi8Yw

* Build the Flatpak against org.freedesktop.Platform 25.08

Runtime branch 24.08 is end-of-life and no longer receives security
updates, so every flatpak update now prints an EOL warning. 25.08 is
the current supported branch on Flathub. The app bundles its own Java
runtime, so the platform bump only changes the base libraries.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WFGQ7wkSPo21itLMHPi8Yw

---------

Co-authored-by: Claude <noreply@anthropic.com>

packaging/aur/kst4contest-git/.SRCINFO

@@ -2,7 +2,7 @@ pkgbase = kst4contest-git
 	pkgdesc = ON4KST Chat Client for VHF/UHF contest operation (git)
 	pkgver = 1.50.0.r356.ge0c1c6b6
 	pkgrel = 1
-	url = https://github.com/praktimarc/kst4contest
+	url = https://github.com/HamRadioOnline/kst4contest
 	arch = x86_64
 	license = GPL-3.0-only
 	makedepends = java-environment=21
@@ -12,7 +12,7 @@ pkgbase = kst4contest-git
 	provides = kst4contest
 	conflicts = kst4contest
 	conflicts = kst4contest-bin
-	source = kst4contest::git+https://github.com/praktimarc/kst4contest.git
+	source = kst4contest::git+https://github.com/HamRadioOnline/kst4contest.git
 	sha256sums = SKIP
 
 pkgname = kst4contest-git