Cleaned up job listings: no more stray bullet, and company logos display properly

Two fixes to how job listings render on /jobs, found live and fixed the same day:

A default browser bullet marker had been rendering next to every job card all along -- easy to miss until it landed right next to the new "source" label we added recently. Removed.

Company logos also weren't displaying well. The rounding fix we shipped earlier today was correct, but a follow-up look found company logos were being squeezed into a box too small for some of the source images, and the surrounding layout wasn't built to resize cleanly around it. We rebuilt the whole listing row with simpler, sturdier markup so this holds up going forward, and logos now render in an 80x80 box.

One honest limitation: a handful of scraped listings only have a very small, oddly-shaped source logo to begin with (a wide wordmark far smaller than a normal square logo), and no amount of layout fixing makes a low-resolution source image look sharp. That's a data-quality gap in what we receive from some job sources, not something CSS can fully solve.