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

compose.yaml

@@ -134,6 +134,33 @@ services:
       retries: 5
       start_period: 10s
 
+  sql-executor:
+    build:
+      context: .
+      dockerfile: Dockerfile.sql-executor
+    restart: always
+    ports:
+      - "4000:4000"
+    environment:
+      - FREESCOUT_DB_HOST=10.136.40.104
+      - FREESCOUT_DB_PORT=3306
+      - FREESCOUT_DB_USER=freescout
+      - FREESCOUT_DB_PASSWORD=5N6fv4wIgsI6BZV
+      - FREESCOUT_DB_NAME=freescout
+      - POSTGRES_HOST=postgres
+      - POSTGRES_PORT=5432
+      - POSTGRES_USER=kb_user
+      - POSTGRES_PASSWORD=${POSTGRES_PASSWORD}
+      - POSTGRES_DB=n8n_kb
+    depends_on:
+      postgres:
+        condition: service_healthy
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:4000/health"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+
 volumes:
   n8n_data:
   traefik_data: