Volume/pan/EQ tab overhaul: one master switch, peer checklist, 16-band parametric EQ

Reworks the per-peer shaping tab (held for next release):

 * Renamed the tab to "Volume, pan and EQ for peers"; the Preferences toggle now defaults ON.
 * Collapsed the two master switches (Enable EQ / Enable pan) into ONE: "Enable volume, pan and
   EQ for all peers" (Alt+E). Volume now obeys it too. PeerDspChain.Build takes a single enabled
   flag; Profile.EnableAllPeerShaping replaces the two bools (old ones kept for load-migration).
 * Peer picker is now a CheckedListBox: ticking a peer shapes them (per-peer bypass via new
   PeerShaping.Enabled, default true); the focused row is the one the controls edit. Effective
   shaping = master switch AND that peer's tick. Letter-nav suppressed so keys never toggle a tick.
 * Three EQ modes, renamed: "3 band simple EQ", "12 band advanced graphic EQ", and the new
   "16 band parametric EQ" (PeerEqMode.Parametric16Band).
 * Parametric EQ: up to 16 user bands, each a boost/cut across a start->end range (PeerShaping
   .ParametricBands; ParametricToPeaking maps range -> peaking centre+Q, shared by DSP and curve).
   Add band dialog (spin-or-type, numeric-only, live preview, OK/Escape); Bands list sorted
   bass->treble reading "X Hz to Y Hz, plus/minus N dB"; Delete key / Delete button, multi-select.
   Set peer EQ to default clears the parametric list too.
 * dB now spoken as words ("plus 3 dB" / "minus 6 dB" / "flat") on the graphic sliders and the
   parametric list, since NVDA users typically have punctuation off and never hear a "+".
 * New unbound machine-wide global shortcut "Toggle volume, pan and EQ for all peers" (not stored
   in any profile) via the hotkey controller + settings store.
 * Renamed the Inputs/outputs "Set volume for all received audio" to "Master receive volume".
 * Added EqCurveControl: a purely-visual EQ response graph (not focusable, invisible to NVDA).
 * Full manual sweep (readme.html + regenerated MANUAL.md).

Build clean; --selftest passes. Deployed to both test folders. Held for next release.

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

src/RemSound.Core/AppConfig.cs

@@ -68,11 +68,12 @@ public sealed class AppConfig
     /// already running quietly". Default false.</summary>
     public bool StartMinimised { get; set; }
 
-    /// <summary>If true, the main window shows a "Pan and EQ" tab (positioned before "Audio profile")
-    /// for setting per-peer panning and EQ. Off by default; toggled by "Show pan and EQ tab" on the
-    /// Preferences General tab. Machine-wide (a UI-visibility preference, like which tabs exist) — the
-    /// pan/EQ VALUES are saved per profile, in <see cref="Profile.PeerShaping"/>.</summary>
-    public bool ShowPanEqTab { get; set; }
+    /// <summary>If true (the default), the main window shows a "Volume, pan and EQ for peers" tab
+    /// (positioned before "Audio profile") for setting per-peer volume, panning and EQ. Toggled by
+    /// "Show the volume, pan and EQ for peers tab" on the Preferences General tab. Machine-wide (a
+    /// UI-visibility preference, like which tabs exist) — the shaping VALUES are saved per profile, in
+    /// <see cref="Profile.PeerShaping"/>.</summary>
+    public bool ShowPanEqTab { get; set; } = true;
 
     /// <summary>If true (the default), RemSound plays the startup cue once, right after this
     /// copy wins the single-instance takeover and before the profile loads. Machine-wide (not
@@ -173,6 +174,10 @@ public sealed class AppConfig
     public HotkeyRecord? SystemMuteToggleHotkey { get; set; }
     public HotkeyRecord? QuickProfileSwitchHotkey { get; set; }
     public HotkeyRecord? SpeakStatusLineHotkey { get; set; }
+    /// <summary>Global shortcut that toggles the "Enable volume, pan and EQ for all peers" master
+    /// switch. Machine-wide and unset by default; NOT stored in any profile (unlike the shaping
+    /// values). The user binds it in Keyboard shortcuts.</summary>
+    public HotkeyRecord? ToggleAllPeerShapingHotkey { get; set; }
 
     /// <summary>True once the one-time "your keyboard shortcuts are now shared across profiles" notice
     /// has been shown (to an upgrader), or silently marked done on a fresh install that had nothing to