Storage: share the card with a phone's browser (#88)

`w` in the Storage App starts a small HTTP server and shows its address,
as a QR code and in letters, with a six-digit code. A browser on the same
network that has typed the code can list, download, upload, make folders
and delete, under the Storage App's rules. The server runs only while that
screen is open. Nothing is encrypted, and the screen says so.

Uploads are streamed to the card under a temporary name and renamed when
whole. Every access to the card is handed to the storage task, 8 KB at a
time, from the server's own task.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

site/content/faq.md

@@ -59,6 +59,10 @@ Yes: it is [open source](https://git.twis.la/twisla/roro9stack) (GPL-3.0). The d
 
 A secure connection takes about 52 KB of the 107 KB the device has, and IRC's takes about 40 KB. Both together do not always fit. See [When a connection says "not enough memory"](/howto/not-enough-memory/).
 
+## How do I copy files to and from my phone?
+
+In the Storage App, press <kbd>w</kbd>: the device serves a small web page to any browser on the same Wi-Fi. Scan the QR code it shows, type the code, and upload or download. Nothing to install. See [From a phone](/guide/storage/#from-a-phone).
+
 ## Do I need an SD card?
 
 For the radio, GNSS position, Wi-Fi tools, IRC chat and Gemini browsing, no. For anything that is *kept*, yes: notes, IRC logs, Wi-Fi scan logs, GNSS Tracks, LoRa captures, saved Gemini pages and update files. See [Find your files on the SD card](/howto/sd-files/).