feat: sign in

[guillermomachado]

What does this do?

Adds sign-in functionality that would work with our BlackMarket API.

Who/what does this impact?

Auth functionality.

How did you test this?

Set the API_URL env variable to https://rs-blackmarket-api.herokuapp.com/api and test sign-in flow.

[github-actions]

💯 Test Coverage

Lines	Statements	Branches	Functions
	52.62% (271/515)	45.58% (98/215)	37.56% (74/197)

😎 Tests Results

Tests	Skipped	Failures	Errors	Time
69	0 💤	0 ❌	0 🔥	27.946s ⏱️

👀 Tests Details • (53%)

File	% Stmts	% Branch	% Funcs	% Lines	Uncovered Line #s
All files	52.62	45.58	37.56	53.15
api/auth	0	100	0	0
use-login.ts	0	100	0	0	19–37
app	0	0	0	0
_layout.tsx	0	0	0	0	20–64
sign-in.tsx	0	100	0	0	11–24
components	54.54	100	50	54.54
login-form.tsx	100	100	50	100