Report and retry Docker resources remove_project could not delete

remove_project_volumes always returned Ok(()) regardless of what actually
happened, making the `if let Err(e)` guarding it at every call site dead
code. remove_project then dropped the project record unconditionally, so a
volume, image or container that failed to delete became permanently
unreachable — confirmed against a real orphaned volume pair found in the
wild (fixes #31).

remove_project_volumes/remove_snapshot_image/remove_container now report
what they could not remove (treating "already gone" as success rather than
a leftover), remove_project surfaces this to the user via a toast, and
before dropping the project record it writes a pending-cleanup record that
startup housekeeping retries automatically on the next launch.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FGjXq6fqtAFHdbhk4f3PfZ

app/src-tauri/src/lib.rs

@@ -257,6 +257,10 @@ pub fn run() {
                     log::info!("Startup housekeeping dropped {} stale rollback pin(s)", reaped);
                 }
                 crate::docker::sweep_orphaned_snapshots_logged("startup").await;
+                // A container/image/volume `remove_project` could not delete
+                // is recorded rather than lost — see triple-c#31 — and this is
+                // the only place anything ever retries it.
+                crate::commands::project_commands::retry_pending_cleanup_logged().await;
             });
 
             // Auto-start web terminal server if enabled in settings