shell migration: fish -> mksh, reorganize bin/, wallpaper cleanup

- replace fish config with .profile (POSIX login) and .mkshrc (interactive)
- organize .local/bin into subdirs: academic, cron, dev, dmenu, history,
  media, misc, monitoring, nnn, security, statusbar, system
- all subdirs added to PATH, scripts callable by name from anywhere
- remove fish config, .config/shell/aliasrc, .config/shell/profile
- consolidate sb-* scripts into statusbar/ (updated stale copies)
- convert wallpapers to webp, slug-WxH naming scheme
- regenerate plan9 solid fills at proper monitor dimensions
- fix larbs -> lazykris path refs across scripts
- remove remapd from both xprofile files
- fix bashism shebangs (11 scripts: #!/bin/sh -> #!/bin/bash)
- update bm-dirs/bm-files for current home layout
- update emoji set to Unicode 15.0 (3655 entries)
- merge push + push-smart into single script with --smart flag
- delete one-off scripts, convert trivial wrappers to aliases

add 10 scripts, remove remapd/remaps

New: dllm, dlog, email, lfub, sb-systemstats, shred, sort, trash, vroid, ytcomments
Removed: remapd, remaps (banned — caused Xorg CPU spikes)