feat: granular CIS MCP server, chat memory compaction, and UX improvements

- Rewrite mcp_cis_server.py with per-section scan tools (IAM, Networking,
  Compute, Logging/Monitoring, Storage, Asset Management) instead of
  monolithic full-tenancy scan — 12 granular tools
- Add cis_reports.py (Oracle CIS Benchmark checker) to backend
- Add chat memory compaction: auto-summarize old messages when history
  exceeds ~8000 tokens, keeping 6 recent messages intact
- Fix GenAI tool use loop: accumulate assistant+tool messages across
  iterations for proper conversation flow (Generic format)
- Remove tenancy confirmation section from system prompt
- Add thinking indicator and button disable in chat UI while waiting
- Add requests dependency for cis_reports.py
- Fix NoneType error in cis_reports.py region filtering

backend/Dockerfile

@@ -15,6 +15,8 @@ RUN pip install --no-cache-dir -r requirements.txt && \
 # Copy app
 COPY app.py .
 COPY cis_runner.py .
+COPY cis_reports.py .
+COPY mcp_cis_server.py .
 
 # Data volume
 RUN mkdir -p /data