[Security] Use a CSPRNG for salts, tokens, and RNG seeding

Password salts and activation tokens were generated with the global SFMT
RNG, which was seeded from a 32-bit timestamp, making registration
salts and activation tokens predictable. The game RNG used the same
timestamp seed across restarts.

Add CryptoUtil backed by OpenSSL RAND_bytes and use it for salt/token
generation and to seed RNG_SFMT with a 64-bit CSPRNG value in both the
client and server. Link libcockatrice_utility against OpenSSL::Crypto.

Took 30 seconds

Took 25 minutes

.ci/Ubuntu26.04/Dockerfile

@@ -16,6 +16,7 @@ RUN apt-get update && \
         libprotobuf-dev \
         libqt6multimedia6 \
         libqt6sql6-mysql \
+        libssl-dev \
         ninja-build \
         protobuf-compiler \
         qt6-image-formats-plugins \