feat: FAM-Edge chat proxy + PyMySQL migration for FAM-UI + config update

- FAM-Edge: add /api/edge/chat proxy endpoint forwarding to local Ollama
  (Ollama port 11434 not exposed externally, FAM-Edge acts as reverse proxy)
- FAM-Core config: edge_url and ollama_url switched from Tailscale IP to
  Oracle public IP (Tailscale firewall blocking between NAS and Oracle)
- FAM-UI: migrate mysql.connector to PyMySQL (same as FAM-Core)
- FAM-UI: cursor(dictionary=True) replaced with cursorclass=DictCursor
- End-to-end chat verified: FAM-Core -> FAM-Edge proxy -> Ollama -> response
  Answer: 今天没有观察到张三 (no events in DB yet, expected)

fam-edge/src/fam_edge/api_gateway/api_gateway.py

@@ -4,6 +4,7 @@ API-Gateway - Flask 蓝图，接收任务
 同时只允许 1 个任务在处理；新任务到达时若当前有任务处理中，返回 429
 """
 import threading
+import requests
 from flask import Blueprint, request, jsonify
 
 from ..logger import setup_logger
@@ -87,3 +88,22 @@ def health():
         "healthy_models": [a.provider_name for a in healthy],
         "processing": _currently_processing
     }), 200
+
+
+@api_bp.route('/api/edge/chat', methods=['POST'])
+def chat_proxy():
+    """代理转发至本地 Ollama /api/generate（Ollama 未对外暴露）"""
+    data = request.get_json(silent=True)
+    if not data:
+        return jsonify({"error": "Invalid JSON"}), 400
+
+    try:
+        resp = requests.post(
+            'http://127.0.0.1:11434/api/generate',
+            json=data,
+            timeout=data.get('options', {}).get('timeout', 120)
+        )
+        return jsonify(resp.json()), resp.status_code
+    except requests.RequestException as e:
+        logger.error(f"Chat proxy error: {e}")
+        return jsonify({"error": f"Ollama unreachable: {e}"}), 502