ci(release): split canary/stable tracks + unified Gitea Releases

A push to main publishes canary builds to canary channels (fast iteration,
unchanged); a single vX.Y.Z tag releases every platform at one version to the
stable channels and attaches all artifacts (.deb/.rpm/.msix/.apk/.aab/.dmg +
flatpak/decky/host-installer) to one Gitea Release. Collapses the
host-v*/win-v*/host-win-v* tag namespaces into v* — the channel split makes the
version-shadow bug structurally impossible (canary and stable are separate repos,
never a shared version line).

- scripts/ci/gitea-release.{sh,ps1}: one idempotent release helper
  (create-or-fetch + delete-before-upload), replacing 3 copy-pasted inline blocks
  and fixing their latent 409-on-reupload bug; prerelease flag auto-derived from
  the tag (an -rc tag won't shadow "Latest")
- channels: apt canary/stable distributions; rpm *-canary/base groups; flatpak
  canary/stable OSTree branches + a 2nd .Canary.flatpakref; generic-registry
  canary/ vs latest/ aliases; Play internal/alpha; Apple TestFlight vs notarized DMG
- android versionName threaded through gradle (versionCode stays run_number);
  Apple canary = TestFlight-only (no DMG/tvOS); canary base bumped to 0.3.0
- docs: new docs-site channels.md (subscribe table + cut-a-release runbook +
  box migration), refreshed ci.md workflow table + packaging READMEs

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packaging/rpm/punktfunk.spec

@@ -17,12 +17,12 @@
 ################################################################################
 
 Name:           punktfunk
-# Version/Release are overridable so CI can stamp a rolling snapshot: a main build passes
-#   --define "pf_version 0.2.0" --define "pf_release 0.ci42.gdeadbee"
-# (Release starting "0." sorts BEFORE the eventual "1" release; base 0.2.0 sits ABOVE the stray
-# 0.1.1), a host-v* tag passes the clean version with "pf_release 1". A plain `rpmbuild` (or COPR)
-# with no defines builds 0.2.0-1.
-Version:        %{?pf_version}%{!?pf_version:0.2.0}
+# Version/Release are overridable so CI can stamp a rolling snapshot: a canary main build passes
+#   --define "pf_version 0.3.0" --define "pf_release 0.ci42.gdeadbee"
+# (Release starting "0." sorts BEFORE the eventual "1" release; the canary base stays one minor
+# ahead of the latest stable), a vX.Y.Z release tag passes the clean version with "pf_release 1".
+# A plain `rpmbuild` (or COPR) with no defines builds 0.3.0-1.
+Version:        %{?pf_version}%{!?pf_version:0.3.0}
 Release:        %{?pf_release}%{!?pf_release:1}%{?dist}
 Summary:        Low-latency desktop/game streaming host (Moonlight-compatible + punktfunk/1)