re-addressing "429: too many requests"

[InteractionEngineer]

I could finally reproduce the 429 myself and went digging. The fix from #92 only touched the validate-while-typing path, but the regular bills/members loader had its own request-burst problem: every onAppear, every mutation, every tab switch fired a fresh Combine pipeline without cancelling the previous one, and a server URL ending in / produced a double slash (https://host//index.php/...) which openresty seems to rate-limit as a separate path.

I removed the leading / from staticPath, made loadBillsAndMembers single-flight (cancel-and-replace via one AnyCancellable), put the tab view models behind @StateObject so they don't get re-allocated on every render, and replaced the .onAppear reloads on the bills and balance tab with .refreshable plus a refresh on scenePhase becoming active.

While I was at it, a few related bugs got in the way of confirming the fix: sortedBills wasn't reacting to new bills (only watching $sortBy), and four views had @State on input properties (BalanceCell, BillCell, WhoPaidView, PersonText) which is why balances and edited bills only updated after reopening the project. Also fixed two background-thread @Published writes that showed up in the console (mutation completion handlers and the QR scan publisher).

Until another occurrence, this merge actually closes #81.

[Copilot]

Pull request overview

Re-addresses the HTTP 429 "Too Many Requests" issue from #81 by eliminating duplicate/burst requests to the Cospend backend and fixing a handful of related SwiftUI state-management bugs that were masking whether the fix worked.

Changes:

• Make loadBillsAndMembers single-flight (cancel-and-replace via a stored AnyCancellable) and add an async refresh() wrapper used by .refreshable; replace .onAppear reloads in BillList/BalanceList with pull-to-refresh + scenePhase reload; hoist tab view models to @StateObject.
• Strip the leading / from ProjectBackend.staticPath so a server URL with a trailing slash no longer produces //, and add a regression test.
• Fix unrelated SwiftUI bugs: sortedBills now reacts to currentProject via CombineLatest; convert @State/@Binding input properties on BalanceCell, BillCell, WhoPaidView, PersonText, PersonsView to let; route background-thread @Published writes through DispatchQueue.main.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
PayForMe/Model/Project.swift	Removes leading slash from staticPath for both backends to avoid // when server URL has a trailing slash.
PayForMe/Services/ProjectManager.swift	Adds single-flight loadCancellable, async refresh() wrapper, and .receive(on: .main) on mutation publishers; cancels in-flight load on project switch.
PayForMe/Views/ContentView.swift	Promotes tab view models to @StateObject and reloads on scenePhase == .active.
PayForMe/Views/BillList/BillList.swift	Replaces .onAppear reload with .refreshable calling ProjectManager.refresh().
PayForMe/Views/BillList/BillListViewModel.swift	Uses CombineLatest($sortBy, $currentProject) so sortedBills updates when bills change.
PayForMe/Views/BillList/BillCell.swift	Switches bill from @State to let; passes plain values to PersonsView.
PayForMe/Views/BillList/PersonsView.swift	Switches bill and members from @Binding to let.
PayForMe/Views/BillDetail/WhoPaidView.swift	Switches members from @State to let.
PayForMe/Views/PersonText.swift	Switches person from @State to let.
PayForMe/Views/Balance/BalanceList.swift	Replaces .onAppear reload with .refreshable; BalanceCell.balance becomes let.
PayForMe/Views/Projects/QRCodes/AddProjectQRViewModel.swift	Routes passwordCorrect, isTestingSubject, and foundCode through the main queue.
PayForMeTests/NetworkRequestTests.swift	Adds regression test verifying a trailing slash in the server URL no longer produces //.

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