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/spin.py

@@ -102,7 +102,8 @@ async def spin_handler(client: Client, message: Message):
         elif message.reply_to_message.text:
             result = await quote_cmd(client, message)
             filename = 'sticker.png' if result[1] else 'sticker.webp'
-            open('downloads/' + filename, 'wb').write(result[0].getbuffer())
+            with open('downloads/' + filename, 'wb') as f:
+                f.write(result[0].getbuffer())
             coro = False
         else:
             filename = 'photo.jpg'