feat: add base_url env vars, iCloud conflict detector, user compose guidance

- utils.py: support OMBRE_DEHYDRATION_BASE_URL and OMBRE_EMBEDDING_BASE_URL
  so Gemini/non-DeepSeek users can configure without mounting a custom config
- docker-compose.user.yml: pass all 4 model/url env vars from .env;
  add commented Gemini example + optional config.yaml mount hint
- ENV_VARS.md: document OMBRE_DEHYDRATION_BASE_URL and OMBRE_EMBEDDING_BASE_URL
- check_icloud_conflicts.py: scan bucket dir for iCloud conflict artefacts
  and duplicate bucket IDs (report-only, no file modifications)

docker-compose.user.yml

@@ -19,7 +19,20 @@ services:
       - OMBRE_API_KEY=${OMBRE_API_KEY}
       - OMBRE_TRANSPORT=streamable-http
       - OMBRE_BUCKETS_DIR=/data
+      # --- Model override (optional) ---
+      # If you use Gemini instead of DeepSeek, set these in your .env:
+      # 如使用 Gemini 而非 DeepSeek，在 .env 里加：
+      #   OMBRE_DEHYDRATION_BASE_URL=https://generativelanguage.googleapis.com/v1beta/openai/
+      #   OMBRE_DEHYDRATION_MODEL=gemini-2.5-flash-lite
+      #   OMBRE_EMBEDDING_BASE_URL=https://generativelanguage.googleapis.com/v1beta/openai/
+      - OMBRE_DEHYDRATION_BASE_URL=${OMBRE_DEHYDRATION_BASE_URL:-}
+      - OMBRE_DEHYDRATION_MODEL=${OMBRE_DEHYDRATION_MODEL:-}
+      - OMBRE_EMBEDDING_BASE_URL=${OMBRE_EMBEDDING_BASE_URL:-}
+      - OMBRE_EMBEDDING_MODEL=${OMBRE_EMBEDDING_MODEL:-}
     volumes:
       # 改成你的 Obsidian Vault 路径，或保持 ./buckets 用本地目录
       # Change to your Obsidian Vault path, or keep ./buckets for local storage
       - ./buckets:/data
+      # (Optional) Mount custom config to override model / API settings:
+      # （可选）挂载自定义配置，覆盖模型和 API 设置：
+      # - ./config.yaml:/app/config.yaml