Fix meme source admin link handling

[ohld]

Summary

• refresh moderator permissions from DB before denying source-admin actions so role grants are not blocked by stale Redis cache
• accept common source link formats such as t.me/..., telegram.me/..., http://t.me/... and links embedded in text
• grant @MearsM (1007266539) moderator/source-management access via migration

Tests

• python -m pytest tests/tgbot/test_meme_source_handler.py tests/tgbot/test_moderator_permissions.py tests/storage/test_etl_candidates.py -q
• python -m ruff check src/tgbot/handlers/moderator src/storage/etl.py tests/tgbot/test_meme_source_handler.py tests/tgbot/test_moderator_permissions.py tests/storage/test_etl_candidates.py alembic/versions/2026-05-25_grant_mearsm_source_moderation.py
• DATABASE_URL=postgresql+asyncpg://app:app@localhost:65432/app REDIS_URL=redis://:myStrongPassword@localhost:36379 ... alembic upgrade head