Auth: Reduce bcrypt cost for faster login on small devices

[lastzero]

As a user of a small device like a NAS or a Raspberry Pi, I would like the cost of the bcrypt password to be lower so that logging in does not take a very long time (or even timeout).

The default password cost (2^number of rounds) of most implementations is 11 and the current cost in PhotoPrism is 14, so we reduce it to 12¹, which is still more secure than what most other applications use:

Cost	Iterations
8	256 iterations
9	512 iterations
10	1,024 iterations
11	2,048 iterations
12	4,096 iterations
13	8,192 iterations
14	16,384 iterations
15	32,768 iterations
16	65,536 iterations

Footnotes

1. Developers can change this value in internal/entity/password.go to use a higher/lower cost in custom builds, depending on their needs. ↩