#280: remove PALETTE_TRUSTED_IP_HEADER, key rate limits on peer address only

Owner follow-up to the #280 fix (PR #284): the trusted-header env var is
gone. clientIP() now uses the peer address exclusively and ignores all
client-supplied IP headers; the env var row is removed from the README.

README.md

@@ -71,7 +71,6 @@ go build -o palette ./cmd/palette
 | `PALETTE_ADMIN_KEY` | generated | Admin key; if unset a 32-char hex key is generated and persisted to `<db-dir>/admin-key` (0600) |
 | `PALETTE_DEFAULT_DARK` | dark on | Default dark mode for new visitors. Set `false`, `0`, or `off` to default to light mode. Visitors who toggle dark mode keep their choice in their browser. |
 | `PALETTE_UNLOCK_SECRET` | random per start | HMAC secret for password-unlock cookies. Set a fixed value to keep unlock sessions across restarts or across replicas. |
-| `PALETTE_TRUSTED_IP_HEADER` | unset | Name of a proxy-controlled client-IP header to key API rate limits on (e.g. `CF-Connecting-IP` when Cloudflare is the ingress; Cloudflare strips any client-supplied value). Unset: rate limits key on the peer address only, and all client-supplied IP headers (X-Forwarded-For, X-Real-Ip) are ignored. (#280) |
 
 An `/admin` page exists for runtime settings, protected by a key set at
 install (`PALETTE_ADMIN_KEY` env var) and resettable locally. See