v5.3.7: Fix sync stall, transaction display, balance updates, and bootstrap snapshots

Sync fixes:
- Extend stall detection beyond IBD to catch post-IBD sync gaps
- Walk-forward inv continuation to avoid CBlockLocator exponential gap loop
- Track walk-forward progress for stall recovery without restarting from scratch

GUI fixes:
- Load transactions synchronously in constructor (deferred QTimer never fired)
- Use beginResetModel/endResetModel instead of deprecated reset()
- Schedule full refresh on TRY_LOCK failure to avoid dropped CT_NEW notifications
- Only update cachedNumBlocks after successful balance check (prevents permanent loss)
- Add GetAllBalances() single-pass balance retrieval with TRY_LOCK

Bootstrap:
- Add trusted snapshot manifest verification for bootstrap archives
- Add IsKnownCheckpoint() to validate manifest against compiled-in checkpoints
- Skip txleveldb rebuild when verified manifest is present

Bump version to 5.3.7 across all packaging manifests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/clientversion.h

@@ -8,7 +8,7 @@
 // These need to be macros, as version.cpp's and triangles-qt.rc's voodoo requires it
 #define CLIENT_VERSION_MAJOR       5
 #define CLIENT_VERSION_MINOR       3
-#define CLIENT_VERSION_REVISION    6
+#define CLIENT_VERSION_REVISION    7
 #define CLIENT_VERSION_BUILD       0
 
 // Converts the parameter X to a string after macro replacement on X has been performed.