- fix: loading items (by scrolling down) is glitching while feeds are refreshing

- ref: switch to the standard logger
- ref: organize "server" package using KonMari method

- ref: drop goquery, switch to cascadia (or `x/net`)
- ref: `getlantern/systray` has too many indirect deps, include+rewrite the code
- ref: `mmcdole/gofeed` has too many indirect deps, drop it
