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

modules/python.py

@@ -53,7 +53,7 @@ async def user_exec(_: Client, message: Message):
 
 # noinspection PyUnusedLocal
 @Client.on_message(filters.command(['ev', 'eval'], prefix) & filters.me)
-async def user_eval(client: Client, message: Message):
+async def user_eval(_client: Client, message: Message):
     if len(message.command) == 1:
         await message.edit("<b>Code to eval isn't provided</b>")
         return