feat: AI Self-Loop 專案骨架 — 爬站健檢版

完整實作建構順序 1-8（rule-based）：
- Task Queue（SQLite）：tasks/attempts/results + claim 防重複
- LLM 後端：OllamaBackend(num_ctx=32768) + LLMRouter
- Prompt Builder（YAML+Jinja2，重試注入 feedback）
- Context Assembler / Output Judge / Feedback Builder
- Loop Controller + Circuit Breaker
- Driver 層（BaseDriver + ApiClientDriver）
- Agent 層（BaseAgent + SiteHealthAgent：爬站/健檢/issue 生成）
- pipeline.py 入口，驗收：pending→done，output/ 落地

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

requirements.txt

@@ -0,0 +1,6 @@
+# --- Loop engine / infra ---
+PyYAML>=6.0          # environments.yaml + prompt templates
+Jinja2>=3.1          # prompt rendering
+requests>=2.31       # api_client driver (HTTP)
+beautifulsoup4>=4.12 # HTML parsing for the crawler agent
+# stdlib used elsewhere: sqlite3, dataclasses, urllib, json, logging