release(v1.7.30-alpha): live install/uninstall progress + cleaner pull waterfall

- Backend: unified pull-progress streaming across primary AND fallback
  registries. Earlier code only streamed for the primary attempt; if it
  failed fast (VPS 404, etc.) the UI froze at 0% until the fallback
  finished. The waterfall now uses a single shared helper that streams
  podman stderr through update_install_progress for every URL tried.
- Backend: PackageDataEntry gains uninstall_stage, set at each phase of
  handle_package_uninstall ("Stopping containers (i/total)",
  "Cleaning up volumes", "Removing app data"). State flips to Removing
  during the pipeline.
- Frontend: MarketplaceAppCard renders the live progress bar with byte
  counts during installs, matching the System Update download bar style.
- Frontend: AppCard renders the live uninstall stage label per app.
  Modal closes immediately on confirm so concurrent uninstalls each
  show their own progress on their own card.
- Cleanup: removed dead helpers (image_candidates, rewrite_for_primary,
  primary_image_url, pull_from_registries_with_skip) made unused by
  the install.rs refactor.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

core/archipelago/src/data_model.rs

@@ -138,6 +138,13 @@ pub struct PackageDataEntry {
     pub installed: Option<InstalledPackageDataEntry>,
     #[serde(rename = "install-progress")]
     pub install_progress: Option<InstallProgress>,
+    /// Live label describing the current uninstall step ("Stopping
+    /// containers (2/5)", "Removing data", …). Set by the uninstall
+    /// pipeline so the UI can show real progress instead of a generic
+    /// "Uninstalling…" spinner. Cleared after the package entry is
+    /// removed.
+    #[serde(rename = "uninstall-stage", skip_serializing_if = "Option::is_none", default)]
+    pub uninstall_stage: Option<String>,
     /// Pinned image version from image-versions.sh when it differs from running version
     #[serde(rename = "available-update", skip_serializing_if = "Option::is_none")]
     pub available_update: Option<String>,