fix: use context managers for file handles to prevent resource leaks (#13514)

## Summary
- Convert bare `open()` calls to `with` context managers or
`Path.read_text()`
- File handles leak if not properly closed, especially on exceptions
- Fixes in crypt.py, sequence2txt_model.py, term_weight.py,
deepdoc/vision/__init__.py

## Test plan
- [x] File operations work correctly with context managers
- [x] Resources properly cleaned up on exceptions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

api/utils/crypt.py

@@ -17,6 +17,7 @@
 import base64
 import os
 import sys
+from pathlib import Path
 from Cryptodome.PublicKey import RSA
 from Cryptodome.Cipher import PKCS1_v1_5 as Cipher_pkcs1_v1_5
 from common.file_utils import get_project_base_directory
@@ -27,7 +28,7 @@ def crypt(line):
     decrypt(crypt(input_string)) == base64(input_string), which frontend and ragflow_cli use.
     """
     file_path = os.path.join(get_project_base_directory(), "conf", "public.pem")
-    rsa_key = RSA.importKey(open(file_path).read(), "Welcome")
+    rsa_key = RSA.importKey(Path(file_path).read_text(), "Welcome")
     cipher = Cipher_pkcs1_v1_5.new(rsa_key)
     password_base64 = base64.b64encode(line.encode('utf-8')).decode("utf-8")
     encrypted_password = cipher.encrypt(password_base64.encode())
@@ -36,7 +37,7 @@ def crypt(line):
 
 def decrypt(line):
     file_path = os.path.join(get_project_base_directory(), "conf", "private.pem")
-    rsa_key = RSA.importKey(open(file_path).read(), "Welcome")
+    rsa_key = RSA.importKey(Path(file_path).read_text(), "Welcome")
     cipher = Cipher_pkcs1_v1_5.new(rsa_key)
     return cipher.decrypt(base64.b64decode(line), "Fail to decrypt password!").decode('utf-8')
 
@@ -51,7 +52,7 @@ def decrypt2(crypt_text):
         decode_data = b16decode(hex_fixed.upper())
 
     file_path = os.path.join(get_project_base_directory(), "conf", "private.pem")
-    pem = open(file_path).read()
+    pem = Path(file_path).read_text()
     rsa_key = RSA.importKey(pem, "Welcome")
     cipher = Cipher_PKCS1_v1_5.new(rsa_key)
     decrypt_text = cipher.decrypt(decode_data, None)