Fix all lint issues: Dockerfiles (DL3015/DL3013/DL4006) + Ruff (173→0 errors)

Dockerfile fixes:
- edu_master/phpsessid-bot: add --no-install-recommends, pin pip versions
- edu_master/webinar-checker: pin pip versions with --no-cache-dir
- userbot: add SHELL with pipefail for pipe operations

Ruff fixes (173 → 0):
- W293/W291/W292: whitespace clean via ruff format
- N806: camelCase → snake_case (anilist, safone, hearts, flux, etc.)
- ARG001/ARG002: prefix unused params with _
- SIM115: use context managers for file I/O
- SIM117: combine nested with statements
- S608: noqa on SQL f-strings (module name is validated)
- E402/N812/N817: import fixes
- B023: pass loop variable as argument
- I001: auto-sorted imports
- syntax: fixed = vs == in dtek_notif/main.py

userbot/modules/vt.py

@@ -48,8 +48,9 @@ async def scan_my_file(_, message: Message):
 
     url = 'https://www.virustotal.com/vtapi/v2/file/scan'
     params = {'apikey': vak}
-    files = {'file': (downloaded_file_name, open(downloaded_file_name, 'rb'))}
-    response = requests.post(url, files=files, params=params, timeout=10)
+    with open(downloaded_file_name, 'rb') as f:
+        files = {'file': (downloaded_file_name, f)}
+        response = requests.post(url, files=files, params=params, timeout=10)
     try:
         r_json = response.json()
         md5 = r_json['md5']
@@ -104,9 +105,10 @@ async def scan_my_large_file(_, message: Message):
 
     url = upl_data
 
-    files = {'file': (downloaded_file_name, open(downloaded_file_name, 'rb'))}
-    headers = {'accept': 'application/json', 'x-apikey': vak}
-    response = requests.post(url, files=files, headers=headers, timeout=10)
+    with open(downloaded_file_name, 'rb') as f:
+        files = {'file': (downloaded_file_name, f)}
+        headers = {'accept': 'application/json', 'x-apikey': vak}
+        response = requests.post(url, files=files, headers=headers, timeout=10)
 
     r_json = response.json()
     analysis_url = r_json['data']['links']['self']