feature(app-overhaul) stabilize routing and add device-wide Headphone EQ + UX refresh

[Vudgekek]

Summary

A broad overhaul of FineTune’s audio pipeline and popup UX.

It improves routing/process stability, removes several long-standing pain points, and adds a more powerful device-focused EQ workflow for everyday use.

Fixes

• Fixed attenuated output on multichannel devices ([Bug] Low output on Topping E2x2 OTG (8ch) while FineTune is active; normal when FineTune is off #105), so channel mapping no longer reduces perceived loudness.
• Fixed output priority behavior ([BUG] Output priority not working #130), so auto-switching now follows the intended priority order.
• Fixed helper-process apps not being processed, so Chromium/Discord-style app trees are handled correctly.
• Fixed the audible processing click on first attach, reducing startup artifacts when audio begins.
• Fixed device edit mode behavior when switching Output/Input tabs, so edit state persists as expected.
• Increased stale app retention timeout, so inactive entries are not cleared too quickly ([Feature Request] Persist audio sources longer & show previous sources with pinning #119).
• Removed dead/unused code paths to reduce maintenance risk and improve runtime clarity.

Features

• Added Parametric Headphone EQ with AutoEQ profile import support ([Feature Request] Parametric EQ with AutoEq Profile Support #121).
• Added a device sample-rate menu and Bluetooth device control actions (Feature request - choose/lock sample rate #15).
• Added an app exclusion menu to quickly skip selected apps from processing.
• Added a button in device edit mode to hide selected devices (Feature Request: Hide unused output devices from list #59).
• Switched EQ scope from app-dependent to device-wide behavior.
• Added dynamic volume/speaker icons based on live volume level (including the menu bar icon).
• Included broader UI refinements and icon updates from #17.

Testing Passed

• Tested with 2+ output devices.
• Tested device hot-plug, including disconnect during active playback.
• Tested with 5+ apps playing audio simultaneously.

[Vudgekek]

Apologies for previous commit spam, force-pushed here to make it more clear what's going on. Also, initially remade this PR because Github had restricted my account's public visibility (old one had to be closed for some reason).

[ronitsingh10]

Hey @Vudgekek — thanks for putting in serious work here. There's a lot of valuable stuff in this PR.

The main challenge is that main has been reorganized since this branch was created — files have moved into subdirectories (Audio/Engine/, Audio/EQ/, Audio/Monitors/, etc.), and there's new infrastructure like BiquadProcessor, CrashGuard, SoftLimiter, OrphanedTapCleanup, and TapResources that this PR would overwrite.

The scope also makes it hard to review and merge safely as one unit. Would you be open to rebasing against latest main and splitting into smaller PRs? That way each piece can be reviewed and merged independently.

[Vudgekek]

Sure thing!