Docs: a page each, and API references for ipx and the directory laid out like docs.rs (#223)

site/gen.mjs writes them from site/api.mjs, which holds each endpoint and type as the handlers
have them, and site/docs.mjs, the guides. A misspelt type in api.mjs fails the build rather than
leaving a name that links nowhere.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

site/guides/install.html

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+<h1>Install ipx and ipx-web</h1>
+<p class="lede">iPX is two containers: <strong>ipx</strong>, which checks your podcasts, downloads them and answers the API, and <strong>ipx-web</strong>, which serves the page and passes the API on to ipx.</p>
+    <p>You need Docker with Compose. There are no published images yet, so you build both from the source:</p>
+<pre><code>git clone https://git.sdf1.net/rays/ipx.git
+cd ipx
+docker build -t ipx .
+docker build -f Dockerfile.web -t ipx-web .</code></pre>
+    <p>The repository has a sample <code>docker-compose.yml</code> that runs both, with the database in SQLite and everything ipx keeps in three folders beside the file:</p>
+<pre><code>services:
+  ipx:
+    image: ipx
+    container_name: ipx
+    restart: unless-stopped
+    environment:
+      PUID: "99"          # who owns the files it writes
+      PGID: "100"
+      TZ: "UTC"
+    ports:
+      - "6881:6881/tcp"   # BitTorrent
+      - "6881:6881/udp"
+    volumes:
+      - ./config:/config  # config.toml, written on first start
+      - ./data:/data      # the database
+      - ./downloads:/downloads
+
+  ipx-web:
+    image: ipx-web
+    container_name: ipx-web
+    restart: unless-stopped
+    environment:
+      IPX_UPSTREAM: "ipx:8099"
+    ports:
+      - "8099:8080"       # the page
+    depends_on:
+      - ipx</code></pre>
+<pre><code>docker compose up -d</code></pre>
+    <p>ipx has no port of its own: everything reaches it through ipx-web, on port 8099. Open <code>http://&lt;your server&gt;:8099</code> and sign in as <strong>admin</strong> with the password <strong>ipodderx</strong>, then change it:</p>
+<pre><code>echo -n 'a good password' | docker exec -i ipx ipx user passwd admin</code></pre>
+    <p>The password is read from what you pipe in, so it stays out of your shell's history.</p>
+
+    <h2>Adding people</h2>
+    <p>An admin adds people in Admin, Accounts, or from the command line:</p>
+<pre><code>echo -n 'their password' | docker exec -i ipx ipx user add sam</code></pre>
+    <p>Each person starts with no podcasts and subscribes to their own. Two people subscribing to the same show cost nothing extra: it is fetched once and each file is kept once.</p>
+
+    <h2>Settings</h2>
+    <p>How often podcasts are checked, how much disk to use, how many new episodes to download and the rest are in Admin on the page, and take effect straight away. <code>/config/config.toml</code> holds only what ipx needs before it can read its database: where downloads go, BitTorrent, and who gets in.</p>
+    <div class="scroll"><table>
+      <thead><tr><th>Environment variable</th><th>What it does</th></tr></thead>
+      <tbody>
+        <tr><td><code>IPX_DATABASE_URL</code></td><td>A <code>postgres://user:password@host:5432/database</code> address, to keep everything in Postgres instead of SQLite</td></tr>
+        <tr><td><code>PUID</code>, <code>PGID</code></td><td>The user and group that own the files ipx writes</td></tr>
+        <tr><td><code>IPX_LOG_FORMAT</code></td><td><code>json</code> logs one JSON object a line, for Loki and the like</td></tr>
+        <tr><td><code>OTEL_EXPORTER_OTLP_ENDPOINT</code></td><td>Sends traces of requests, checks and downloads to an OpenTelemetry collector; set <code>WEB_TRACING=on</code> on ipx-web too</td></tr>
+        <tr><td><code>IPX_UPSTREAM</code></td><td>On ipx-web: where ipx is, <code>ipx:8099</code> by default</td></tr>
+      </tbody>
+    </table></div>
+
+    <h2>Reaching it from outside</h2>
+    <p>The page is plain HTTP. If anyone will reach it from outside your network, put HTTPS in front of it: a reverse proxy you already run, or a Cloudflare tunnel. People can then sign in through Cloudflare Access or Authentik instead of a password; <a href="https://git.sdf1.net/rays/ipx/src/branch/main/docs/sso.md">single sign-on</a> says how.</p>
+
+    <h2>Updating</h2>
+<pre><code>git pull
+docker build -t ipx .
+docker build -f Dockerfile.web -t ipx-web .
+docker compose up -d</code></pre>
+    <p>Your podcasts, accounts and downloads are in the three folders and are kept.</p>