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

edu_master/webinar-checker/Dockerfile

@@ -3,7 +3,7 @@ FROM python:3.11-slim
 WORKDIR /app
 
 # Install dependencies
-RUN pip install --upgrade pip && pip install playwright==1.56.0 redis requests "python-telegram-bot[job-queue]"
+RUN pip install --no-cache-dir --upgrade pip && pip install --no-cache-dir playwright==1.56.0 redis==5.2.1 requests==2.32.3 "python-telegram-bot[job-queue]==21.10"
 
 COPY checker.py .