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>

clients/android/app/build.gradle.kts

@@ -26,7 +26,9 @@ android {
         targetSdk = 36
         val vCode = (props.getProperty("VERSION_CODE") ?: System.getenv("VERSION_CODE"))
         versionCode = vCode?.toInt() ?: 1
-        versionName = "0.0.2" // bumped for first Play Store release
+        // versionName is the single project version, threaded from CI (a vX.Y.Z release or a
+        // canary string). versionCode stays the monotonic run number (Play rejects regressions).
+        versionName = (props.getProperty("VERSION_NAME") ?: System.getenv("VERSION_NAME")) ?: "0.0.2"
         ndk { abiFilters += listOf("arm64-v8a", "x86_64") }
     }