Bump to v3.1.2: tray icon re-stamps on state change, recording shows as a flag

- Tray icon now re-registers itself (hide+re-show) whenever the meaningful
  state changes — peer connect/drop, send/receive toggle, recording
  start/stop — so the name a screen reader announces stays in step with
  the live state. Fixes the persistent "no peers" then "1 peer" double
  announcement that the old "show window then minimise again" trick used
  to clear by hand. Same root cause as the v3.1.1 stuck-tooltip fix, just
  exposed when the state changes a moment after the icon appears.
- Recording shows as a plain "recording" flag in the tray rather than a
  live timer. A ticking timer would have either flickered the icon once a
  second or left a screen reader announcing a stale time next to the live
  one. Removed the now-dead FormatRecordingElapsed helper.
- Bundles the earlier Win7 updater fix (6cbde0d): a failed secure
  connection is no longer mislabelled as "you're up to date".
- About box, RELEASE_NOTES.md, readme.html and MANUAL.md updated to match.

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

src/RemSound.App/AboutDialog.cs

@@ -20,6 +20,44 @@ internal sealed class AboutDialog : Form
     /// updates" path.</summary>
     private const string ReleaseNotes =
         """
+        RemSound v3.1.2
+
+        A small accessibility fix for the system tray
+        icon, plus a clearer "check for updates" message
+        for Windows 7.
+
+        The tray icon's double announcement: if you use a
+        screen reader, the tray icon could read out two
+        states one after the other — for example "no peers"
+        and then "1 peer" — every time you landed on it. It
+        always happened in that same order. Windows stamps
+        a tray icon's name at the moment the icon appears,
+        which on a fresh start is a second before your other
+        machine has reconnected — so the name was frozen as
+        "no peers" while only the hover text caught up to
+        "1 peer". RemSound now refreshes the icon itself
+        whenever something real changes — a peer connecting
+        or dropping, sending or receiving switching on or
+        off, a recording starting or stopping — so the
+        screen reader hears a single, current state.
+
+        Recording in the tray: while a recording is running
+        the tray now simply says "recording" rather than
+        counting the seconds. A live timer would have made
+        the icon flicker or read out a stale time; the exact
+        length is on the main window if you need it.
+
+        Windows 7 update message: on a Windows 7 machine
+        that can't make a secure connection to the update
+        server, "Check for updates" used to say "you're on
+        the latest version", which was misleading. It now
+        explains that the secure connection failed and points
+        to the Windows updates that fix it, with a manual
+        download link as a fallback. Windows 10 and 11 were
+        never affected.
+
+        Everything else from v3.1 is unchanged.
+
         RemSound v3.1.1
 
         Hot-fix for a small but annoying bug with the system