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/flux.py

@@ -9,9 +9,9 @@ from utils.scripts import format_exc, progress
 
 
 def schellwithflux(args):
-    API_URL = 'https://randydev-ryuzaki-api.hf.space/api/v1/akeno/fluxai'
+    api_url = 'https://randydev-ryuzaki-api.hf.space/api/v1/akeno/fluxai'
     payload = {'user_id': 1191668125, 'args': args}  # Please don't edit here
-    response = requests.post(API_URL, json=payload, timeout=10)
+    response = requests.post(api_url, json=payload, timeout=10)
     if response.status_code != 200:
         print(f'Error status {response.status_code}')
         return None
@@ -19,7 +19,7 @@ def schellwithflux(args):
 
 
 @Client.on_message(filters.command('fluxai', prefix) & filters.me)
-async def imgfluxai_(client: Client, message: Message):
+async def imgfluxai_(_client: Client, message: Message):
     question = message.text.split(' ', 1)[1] if len(message.command) > 1 else None
     if not question:
         return await message.reply_text('Please provide a question for Flux.')