v5 pre-release: multi-track drift fix, more self-tests, logging, CLI, version bump

Multi-track recording drift fix (Ed's question — can the separate tracks drift over an hour?):
 * Root: FlushPeerTracks skipped a peer that produced no samples in a render block, so a peer that
   went quiet long enough for its session to be pruned (>4 s idle) would have its track fall behind
   and desync. Now every peer track is padded to a full render block each cycle (silence when the
   peer produced nothing), so all peer tracks stay sample-locked to the single render clock — they
   can't drift apart however long the recording runs, and all end the same length. Same padding for
   the single-file bypass path. OnRecordBlockComplete now carries the block's float count.
   (The peer tracks are already resampled to the render clock per peer, so this makes peer-to-peer
   sync exact; your own "me" track is capture-clocked — same soundcard for capture+playback = same
   clock = no drift, different interfaces can drift slightly.)

 * Self-test: two new steps — "Per-peer shaping DSP" (PeerDspChain unity/master-off/volume/parametric
   + ParametricToPeaking) and "v5 settings and shaping round-trip" (AppConfig defaults, NamedPeers,
   MainTabOrder, parametric PeerShaping, recording default = Both).
 * Logging (gated by the logging checkbox): master shaping switch, EQ-mode change, parametric band
   add/delete, peer rename/clear/delete, and the applied Appearance settings after Preferences close.
 * CLI: --list-profiles and --list-named-peers (read-only), in --help.
 * Version bumped to 5.0; About-box changelog, RELEASE_NOTES.md and README updated for v5.

Build clean; --selftest passes.

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

src/RemSound.App/AboutDialog.cs

@@ -20,6 +20,18 @@ internal sealed class AboutDialog : Form
     /// updates" path.</summary>
     private const string ReleaseNotes =
         """
+        RemSound v5.0
+
+        A big one. Shape each person, record everyone separately, name your peers, and make the window your own.
+
+        Shape each peer. A new "Volume, pan and EQ for peers" tab lets you set how loud each connected person is, lean them left or right, and change their tone with an equaliser — a simple 3-band, a 12-band graphic, or a full 16-band parametric where you place each band yourself. It's all live, adds no delay, and what you dial in is captured in your recordings too.
+
+        Record everyone on their own track. Recording can now save each connected peer to its own separate file, so you can take a jam or a chat away and mix the parts afterwards.
+
+        Name your peers. Give the people you connect to friendly names that stick to their machine for good, and a new details view shows who's connected, for how long, and what they're sending. Manage them all under Options, Manage named peers.
+
+        Make it yours. RemSound now follows your Windows light or dark theme, has a fresh look and its own icon, and a new Appearance tab in Preferences lets you reorder or hide the window's tabs. Jump straight to any tab with Ctrl and its number.
+
         RemSound v4.9
 
         Lock a profile to fixed addresses.