feat: App filter popover, source metadata & copied app source icon

[andonits]

Summary

• Replaces the compact app filter UI with a popover: a master “All apps” switch plus per-app toggles on a narrow, scrollable panel (AppFilterPopover.swift).
• Captures and persists richer copy source context (SourceContext on ClipboardItem, SourceResolver, ClipboardWatcher) so list rows can show app vs browser badges where available.
• Adds AppIconCache for sharper, safe icon reuse in list and filter rows (ClipboardItemRow updates).
• Fixes “All apps” off behavior by using an optional whitelist (Set<String>?) so the UI no longer snaps back when everything is disabled.
• Updates .gitignore to exclude .idea/ and copy_source_label_plan.md so local IDE and planning files are not committed.

Demo

Screen.Recording.2026-05-15.at.12.09.20.mov

Test plan

• History window → open filter popover: layout, scrolling, row hover, toggles behave as expected.
• Toggle All apps off → empty list until at least one app is enabled; toggle All apps on → full history returns.
• Per-app toggles → list only shows items from allowed sources; unknown/missing source handling still makes sense.
• Copy from a few apps (and a supported browser if applicable) → new items show appropriate source badges/icons.
• xcodebuild/Run in Xcode (macOS) succeeds.

[andonits]

@samirpatil2000 Made a small improvement where you can see the app or browser of the copied text / image. Included a filter lets you filter by specific apps as well. Will appreciate you feedback and review

[samirpatil2000]

Hey @andonits, thanks so much for taking the time to contribute and for putting so much thought into this – really appreciate it.

I like the core idea a lot, but it feels a bit more developer‑focused than where I want to take Buffer right now. My aim is to keep the app simpler and a bit more general‑purpose, rather than leaning too much into power‑user/dev tooling.

I had a similar idea earlier and ended up shipping a new feature that lets you search/filter based on tags instead. You can check it out here: https://github.com/samirpatil2000/Buffer/releases/tag/buffer-v2.0.0

Thanks again for the PR and for helping improve the project – your contributions and ideas really add value.