feat: add web search block functionality and integrate with existing plugins

- Introduced a new web search block plugin to handle web search queries and results.
- Updated copilot, doc block, and pro block plugins to include web search context in AI completions.
- Implemented utility functions for parsing and building web search markdown.
- Enhanced API to support web search requests and responses.
- Added configuration for web search URL and timeout settings.
- Updated size limit checks to account for web search content.

backend/risk_config.py

@@ -74,6 +74,10 @@ class RiskConfig:
     pro_max_input_chars: int
     pro_max_output_tokens: int
     pro_temperature: float
+    web_search_model: str
+    web_search_max_input_chars: int
+    web_search_max_output_tokens: int
+    web_search_temperature: float
     compress_max_input_chars: int
     compress_max_output_tokens: int
     ocr_max_input_bytes: int
@@ -128,6 +132,10 @@ def load_risk_config() -> RiskConfig:
         pro_max_input_chars=_int_env("RISK_PRO_MAX_INPUT_CHARS", 48000),
         pro_max_output_tokens=_int_env("RISK_PRO_MAX_OUTPUT_TOKENS", 2048),
         pro_temperature=_float_env("RISK_PRO_TEMPERATURE", 0.6),
+        web_search_model=_str_env("RISK_WEB_SEARCH_MODEL", os.getenv("LLM_MODEL", "gpt-4.1-mini")),
+        web_search_max_input_chars=_int_env("RISK_WEB_SEARCH_MAX_INPUT_CHARS", 128000),
+        web_search_max_output_tokens=_int_env("RISK_WEB_SEARCH_MAX_OUTPUT_TOKENS", 4096),
+        web_search_temperature=_float_env("RISK_WEB_SEARCH_TEMPERATURE", 0.4),
         compress_max_input_chars=_int_env("RISK_COMPRESS_MAX_INPUT_CHARS", 128000),
         compress_max_output_tokens=_int_env("RISK_COMPRESS_MAX_OUTPUT_TOKENS", 1536),
         ocr_max_input_bytes=_int_env("RISK_OCR_MAX_INPUT_BYTES", 10 * 1024 * 1024),