feat: add theme management with light and dark modes

- Implemented a new composable `useTheme` for managing theme state.
- Added functions to read and write theme preference to local storage.
- Applied theme styles to the DOM based on user preference.
- Introduced a toggle function to switch between light and dark themes.

refactor: enhance copilot plugin functionality

- Improved request handling with sequence and document versioning.
- Refactored ghost text handling to improve clarity and efficiency.
- Updated markdown insertion logic to handle parsed content more robustly.
- Enhanced error handling and logging for better debugging.

style: update global styles for light and dark themes

- Defined CSS variables for light and dark themes to streamline styling.
- Improved overall styling consistency and responsiveness.
- Added transitions for smoother theme changes and interactions.

backend/llm.py

@@ -1,6 +1,7 @@
 import os
 import time
 import logging
+from datetime import datetime
 import ollama
 from dotenv import load_dotenv
 
@@ -58,6 +59,7 @@ async def call_ollama(prompt: str, *, tag: str = "default", temperature: float =
     调用 Ollama API 并返回 content 和 thinking。
     """
     start = time.perf_counter()
+    start_dt = datetime.now()
     logger.info(
         "[LLM][%s] request model=%s host=%s prompt_chars=%d temp=%.2f",
         tag,
@@ -79,11 +81,25 @@ async def call_ollama(prompt: str, *, tag: str = "default", temperature: float =
         )
     except Exception:
         elapsed_ms = (time.perf_counter() - start) * 1000
+        end_dt = datetime.now()
+        logger.info(
+            "[LLM][%s] call_time [%s --> %s]",
+            tag,
+            start_dt.strftime("%H:%M:%S"),
+            end_dt.strftime("%H:%M:%S"),
+        )
         logger.exception("[LLM][%s] request failed after %.1fms", tag, elapsed_ms)
         raise
 
     content, thinking = _extract_message(response)
     elapsed_ms = (time.perf_counter() - start) * 1000
+    end_dt = datetime.now()
+    logger.info(
+        "[LLM][%s] call_time [%s --> %s]",
+        tag,
+        start_dt.strftime("%H:%M:%S"),
+        end_dt.strftime("%H:%M:%S"),
+    )
     logger.info(
         "[LLM][%s] response in %.1fms response_type=%s content_chars=%d thinking_chars=%d",
         tag,
@@ -100,6 +116,7 @@ async def call_ollama(prompt: str, *, tag: str = "default", temperature: float =
 
 async def call_vlm_ocr(image_bytes: bytes, language: str = 'auto') -> str:
     start = time.perf_counter()
+    start_dt = datetime.now()
     logger.info(
         "[VLM][ocr] request model=%s host=%s image_bytes=%d language=%s",
         VLM_MODEL,
@@ -121,11 +138,23 @@ async def call_vlm_ocr(image_bytes: bytes, language: str = 'auto') -> str:
         )
     except Exception:
         elapsed_ms = (time.perf_counter() - start) * 1000
+        end_dt = datetime.now()
+        logger.info(
+            "[VLM][ocr] call_time [%s --> %s]",
+            start_dt.strftime("%H:%M:%S"),
+            end_dt.strftime("%H:%M:%S"),
+        )
         logger.exception("[VLM][ocr] request failed after %.1fms", elapsed_ms)
         raise
 
     content, thinking = _extract_message(response)
     elapsed_ms = (time.perf_counter() - start) * 1000
+    end_dt = datetime.now()
+    logger.info(
+        "[VLM][ocr] call_time [%s --> %s]",
+        start_dt.strftime("%H:%M:%S"),
+        end_dt.strftime("%H:%M:%S"),
+    )
     logger.info(
         "[VLM][ocr] response in %.1fms response_type=%s content_chars=%d thinking_chars=%d",
         elapsed_ms,