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>

snap/snapcraft.yaml

@@ -1,6 +1,6 @@
 name: triangles
 base: core22
-version: '5.3.6'
+version: '5.3.7'
 summary: Cryptographic Triangles (TRI) cryptocurrency wallet
 description: |
   Privacy-focused cryptocurrency featuring Proof-of-Stake consensus,
@@ -51,10 +51,10 @@ apps:
 parts:
   triangles:
     plugin: dump
-    source: https://github.com/SamiAhmed7777/triangles_v5/releases/download/v5.3.6/Cryptographic-Triangles-v5.3.6-linux-x64-qt
+    source: https://github.com/SamiAhmed7777/triangles_v5/releases/download/v5.3.7/Cryptographic-Triangles-v5.3.7-linux-x64-qt
     source-type: file
     organize:
-      Cryptographic-Triangles-v5.3.6-linux-x64-qt: bin/triangles-qt
+      Cryptographic-Triangles-v5.3.7-linux-x64-qt: bin/triangles-qt
     stage-packages:
       - libqt5widgets5
       - libqt5gui5
@@ -73,10 +73,10 @@ parts:
 
   trianglesd:
     plugin: dump
-    source: https://github.com/SamiAhmed7777/triangles_v5/releases/download/v5.3.6/Cryptographic-Triangles-v5.3.6-linux-x64-daemon
+    source: https://github.com/SamiAhmed7777/triangles_v5/releases/download/v5.3.7/Cryptographic-Triangles-v5.3.7-linux-x64-daemon
     source-type: file
     organize:
-      Cryptographic-Triangles-v5.3.6-linux-x64-daemon: bin/trianglesd
+      Cryptographic-Triangles-v5.3.7-linux-x64-daemon: bin/trianglesd
 
   desktop-entry:
     plugin: dump