Fill the remaining gaps: badge upload, radio tools, VPN, writeable boxes

Built the admin tools previously listed as missing:
- Badge upload (/admin/badges): uploads a <code>.gif into the emulator's
  badge dir via BADGE_UPLOAD_DIR (node:fs); validated code/type/size,
  logged. Made configurable rather than skipped.
- Radio tools: /admin/radio/api-keys (CRUD, server-generated keys),
  /admin/radio/autodj (Auto-DJ playlist CRUD), /admin/radio/embed (embed
  snippet generator), /admin/radio/points (points settings),
  /admin/radio/monitoring (live stream/now-playing/listeners status).
  radio_api_keys + radio_auto_dj_playlist already had real columns.
- /admin/vpn: VPN/proxy detection config (block toggle + provider + key),
  complementing /admin/ip's raw blacklist.
- Writeable boxes: new website_writeable_boxes table (model + migration
  0006) + /admin/writeable-boxes CRUD; active boxes render on the public
  home page. env: BADGE_UPLOAD_DIR.

Verified live (prod, amx_test): all 8 pages render with real data; a test
writeable box appeared on the public home and was reverted. tsc 0,
vitest 49/49, next build 0 (7 new admin routes).

.env.example

@@ -22,6 +22,11 @@ CONVERT_PASSWORDS=false
 # column). Existing accounts in either format still verify on login.
 PASSWORD_HASH=bcrypt
 
+# Filesystem directory the badge uploader (/admin/badges) writes <code>.gif into
+# — the emulator's badge image folder (e.g. .../assets/c_images/album1584).
+# Leave unset to disable badge uploads.
+BADGE_UPLOAD_DIR=
+
 # RCON link to the Arcturus emulator
 RCON_HOST=127.0.0.1
 RCON_PORT=3001