fix: resolve MariaDB collation error by switching from mysql-connector to PyMySQL

- Replace mysql-connector-python with PyMySQL driver for better MariaDB compatibility
- PyMySQL handles utf8mb4_0900_ai_ci collation properly without errors
- Update Dockerfile.sql-executor to install PyMySQL and psycopg2-binary
- Refactor sql-query-executor.py to use PyMySQL API (pymysql.connect, DictCursor)
- Verified sql-executor service with SELECT, INSERT, UPDATE operations on Freescout DB
- Add n8n workflow definitions: workflow-a-http.json and workflow-b-http.json
  * Workflow A: Polls unprocessed conversations, analyzes with LiteLLM, saves suggestions
  * Workflow B: Polls approved suggestions, executes Baramundi jobs or email replies
- Update compose.yaml with sql-executor service configuration and dependencies

All SQL operations now execute successfully against MariaDB 11.3.2

Dockerfile.sql-executor

@@ -0,0 +1,19 @@
+FROM python:3.11-slim
+
+WORKDIR /app
+
+# Install dependencies
+RUN pip install --no-cache-dir flask PyMySQL psycopg2-binary
+
+# Copy the SQL executor script
+COPY scripts/sql-query-executor.py /app/app.py
+
+# Expose port
+EXPOSE 4000
+
+# Health check
+HEALTHCHECK --interval=10s --timeout=5s --retries=5 \
+  CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:4000/health').read()"
+
+# Run the app
+CMD ["python", "app.py"]