Add case-insensitive path validation for Windows/Docker compatibility, improve error handling in file API with binary file support and enhanced logging for path resolution and file read operations

backend/main.py

@@ -191,12 +191,29 @@ def _resolve_safe_path(vault_root: Path, relative_path: str) -> Path:
     Raises:
         HTTPException(403): When the resolved path escapes the vault root.
     """
-    resolved = (vault_root / relative_path).resolve()
-    vault_resolved = vault_root.resolve()
+    # Construct the full path without resolving symlinks first
+    full_path = vault_root / relative_path
+    
+    # Resolve both paths to handle symlinks
     try:
+        resolved = full_path.resolve(strict=False)
+        vault_resolved = vault_root.resolve(strict=False)
+    except Exception as e:
+        logger.error(f"Path resolution error - vault_root: {vault_root}, relative_path: {relative_path}, error: {e}")
+        raise HTTPException(status_code=500, detail=f"Path resolution error: {str(e)}")
+    
+    # Check if resolved path is within vault using string comparison (case-insensitive on Windows)
+    try:
+        # This will raise ValueError if resolved is not relative to vault_resolved
         resolved.relative_to(vault_resolved)
     except ValueError:
-        raise HTTPException(status_code=403, detail="Access denied: path outside vault")
+        # Try case-insensitive comparison for Windows/Docker compatibility
+        resolved_str = str(resolved).lower()
+        vault_str = str(vault_resolved).lower()
+        if not resolved_str.startswith(vault_str):
+            logger.warning(f"Path outside vault - vault: {vault_resolved}, requested: {relative_path}, resolved: {resolved}")
+            raise HTTPException(status_code=403, detail="Access denied: path outside vault")
+    
     return resolved
 
 
@@ -529,10 +546,18 @@ async def api_file(vault_name: str, path: str = Query(..., description="Relative
 
     try:
         raw = file_path.read_text(encoding="utf-8", errors="replace")
-    except PermissionError:
+    except PermissionError as e:
+        logger.error(f"Permission denied reading file {path}: {e}")
         raise HTTPException(status_code=403, detail=f"Permission denied: cannot read file {path}")
+    except UnicodeDecodeError:
+        # Binary file - try to read as binary and decode with errors='replace'
+        try:
+            raw = file_path.read_bytes().decode("utf-8", errors="replace")
+        except Exception as e:
+            logger.error(f"Error reading binary file {path}: {e}")
+            raise HTTPException(status_code=500, detail=f"Cannot read file: {str(e)}")
     except Exception as e:
-        logger.error(f"Error reading file {path}: {e}")
+        logger.error(f"Unexpected error reading file {path}: {e}")
         raise HTTPException(status_code=500, detail=f"Error reading file: {str(e)}")
     
     ext = file_path.suffix.lower()