pithos.sia: account switching, the account/user/bucket model, saved keys

Pithos 0.3.4 shows and labels the Sia account and can switch and restore accounts; 0.3.2 saves keys to an encrypted file. New feature card, a Users & keys card that mentions saved keys, and two FAQs: what a Sia account, an S3 user and a bucket are, and how switching accounts keeps the old one's data.

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     <div class="grid">
       <div class="card"><div class="ic">🔗</div><h3>Guided setup</h3><p>A step-by-step guide takes you from a free Sia Storage account to a working S3 key. Pithos opens the approval page for you and carries on by itself the moment you approve.</p></div>
       <div class="card"><div class="ic">🔒</div><h3>Locked with your PIN</h3><p>In Theseus, Pithos opens with your vault PIN. Three wrong tries and Theseus asks for your master password instead. Lock the vault and Pithos locks with it.</p></div>
-      <div class="card"><div class="ic">🔑</div><h3>Users &amp; access keys</h3><p>Create a user per app or person. Issue and revoke keys, and copy ready-made config for the aws CLI, rclone or environment variables.</p></div>
+      <div class="card"><div class="ic">🔑</div><h3>Users &amp; access keys</h3><p>Create a user per app or person. Issue and revoke keys, copy ready-made config for the aws CLI, rclone or environment variables, and save keys to an encrypted file protected by a password or your Theseus vault.</p></div>
+      <div class="card"><div class="ic">🔁</div><h3>Switch Sia accounts</h3><p>See which Sia account your storage runs on and give it a name. Switch to another account any time: the old one's users, keys and buckets are set aside on your computer, never deleted, and restore with one click.</p></div>
       <div class="card"><div class="ic">🗂️</div><h3>Buckets &amp; files</h3><p>Browse any user's buckets, drag files in, download them, delete folders, and make a bucket public-read when you want to serve files.</p></div>
       <div class="card"><div class="ic">📤</div><h3>Share links</h3><p>Signed links that work without a key and expire after an hour, a day or a week.</p></div>
       <div class="card"><div class="ic">📈</div><h3>Upload pipeline</h3><p>See what is still buffered locally, what is already on Sia, and anything that failed. Flush the buffer on demand.</p></div>
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     <details class="faq"><summary>What does it cost?</summary><p>Pithos is free and open source. Storage is billed by your Sia indexer, for example sia.storage.</p></details>
     <details class="faq"><summary>Which s3d version do I need?</summary><p>v0.2.0 or newer. Pithos offers to install the right one for you and tells you when yours is too old.</p></details>
     <details class="faq"><summary>I already run s3d as a service. Can Pithos manage it?</summary><p>Yes. Pithos uses the same config file a hand-run s3d uses. If s3d is already running, Pithos shows it as external, reads its stats and leaves the process alone.</p></details>
+    <details class="faq"><summary>What is the difference between a Sia account, an S3 user and a bucket?</summary><p>The <b>Sia account</b> (for example on sia.storage) pays for the space; your s3d is connected to one. <b>S3 users</b> are logins on your own s3d, each with its own access keys, so you can give an app its own key and revoke it alone. A <b>bucket</b> is a top-level storage container, like a drive, owned by one user; folders inside it are just part of each file's name.</p></details>
+    <details class="faq"><summary>Can I switch to a different Sia account?</summary><p>Yes, under Sia connection › Switch Sia account. s3d connects to the new account and starts empty. The previous account keeps its files, and its users, keys and buckets are set aside on your computer so you can restore them later. Pithos warns you first if uploads are still on their way to Sia.</p></details>
     <details class="faq"><summary>What if I forget my PIN?</summary><p>After three wrong tries Theseus asks for your master password, which always works. You can set a new PIN any time in Theseus Settings › Passwords.</p></details>
     <details class="faq"><summary>Is there a size limit?</summary><p>Uploads from the Pithos window are capped at 5 GiB per file for now. S3 clients such as aws and rclone use multipart uploads and go well beyond that.</p></details>
     <details class="faq"><summary>Why the name?</summary><p>A pithos was the great storage jar of the ancient Greek world, where a household kept what it could not afford to lose.</p></details>