Per-peer pan + EQ ("Pan and EQ" tab) — off by default, held for next release

New feature (Ed's jam-mixing request): pan and EQ each peer's signal independently.

Engine (zero added latency — per-sample, applied to each peer's isolated block just
before the mix): PeerDspChain (balance pan + RBJ biquad EQ) built on the UI thread and
swapped onto SessionPlayout via a volatile reference; PlayoutEngine remembers it per
address so a reconnecting peer keeps its shaping; AudioReceiver.SetPeerDsp facade.

Model: per-profile PeerShaping dict (keyed by peer address) + EnablePan/EnableEqForPeers
master switches; machine-wide AppConfig.ShowPanEqTab. Fixed band layouts in PeerEqBands
(3-band tone control: bass/mids/treble shelves+bell; 10-band ISO graphic EQ), +/-12 dB.

UI: a "Pan and EQ" tab (before Audio profile, shown only when ShowPanEqTab is on) with
the two enables, a connected-peer picker, a pan slider (balance, keeps stereo), a
"reset EQ" button (clears both modes' bands, leaves pan), a 3/10-band mode picker and its
band sliders — all TrackBars (arrow + page-up/down), updating in real time and saved per
profile. Sliders set a friendly AccessibleName on change (pan centre/left/right %, band
dB). "Show the Pan and EQ tab" checkbox added to Preferences > General.

Everything is off by default (tab hidden, both enables off), so this is dormant for all
users until switched on. Builds clean. Pending Ed's hands-on testing before release.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/RemSound.Core/Profile.cs

@@ -183,6 +183,19 @@ public sealed class Profile
     /// (the connection simply waits or drops rather than moving). Off by default. (#17)</summary>
     public bool LockPeerAddresses { get; set; }
 
+    // === Per-peer pan and EQ (jam mixing) ===
+    /// <summary>Master switch for this profile: apply each connected peer's saved PAN. Off by default.
+    /// The pan values themselves live in <see cref="PeerShaping"/>.</summary>
+    public bool EnablePanForPeers { get; set; }
+
+    /// <summary>Master switch for this profile: apply each connected peer's saved EQ. Off by default.</summary>
+    public bool EnableEqForPeers { get; set; }
+
+    /// <summary>Per-peer pan + EQ, keyed by the SAME peer-entry string used in
+    /// <see cref="SelectedConnectedPeers"/> (user text / discovery label / address:port). A peer with
+    /// no entry gets centre pan and flat EQ. Empty on a fresh profile.</summary>
+    public Dictionary<string, PeerShaping> PeerShaping { get; set; } = new();
+
     // === Hotkeys ===
     public HotkeyRecord? ReceiveMuteHotkey { get; set; }
     public HotkeyRecord? SendMuteHotkey { get; set; }