Fix git not found error crashing document uploads in container

Install git in Docker image and wrap all subprocess git calls in
try/except so a missing or failing git binary never kills an upload
that already succeeded.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude/agents/HEARTBEAT.md

@@ -87,7 +87,7 @@ VALUES (
   '752cebdd-6748-4a04-aacd-c7ab0294ef33',
   'agent_completion',
   'סוכן סיים משימה — נדרשת בדיקה והחלטה על הצעד הבא',
-  'pending',
+  'queued',
   'agent'
 );"
 ```