My road to ML-KEM-768 over X25519 for my messaging app

Eight months ago I started working on a messaging app as an hobby to see how difficult it is. One thing led to another and then I was obsessed with the idea of having it Post-quantum ready. It is well known that Signal works in that regard but from my perspective it isn't full E2EE. Boiling it down to small stuff - why I chose ML-KEM-768 instead of X25519. The "harvest now, decrypt later" problem X25519 is an elliptic curve Diffie-Hellman on Curve25519. Its security rests on the disc...