[ci] Tighten mypy on crypto/ + security/ post-MVP

[jdev-02]

Surfaced during #5.

pyproject.toml currently has ignore_errors = true for crypto.* and security.* because the existing code there has missing type annotations under mypy strict.

Not Jon's place to retype Satriyo's lane mid-hackathon. Track for post-MVP cleanup.

When done: remove the two override blocks from pyproject.toml, type up the missing annotations, run mypy crypto security --strict clean.

Owner: @aleens-labs (post-hackathon).