Upgrade to matrix-js-sdk 41.5.0; add device verification

Upgrades matrix-js-sdk from 34.13.0 to 41.5.0. This crosses the v37
removal of the legacy libolm crypto stack, so E2EE is migrated to the
Rust crypto implementation. Also adds device verification, cross-signing
setup, and authenticated media support.

Dependencies
- Bump matrix-js-sdk ^34.13.0 -> ^41.5.0; require Node.js >= 22.
- Drop the `olm` dependency (legacy crypto only); add `fake-indexeddb`.

Rust crypto
- Replace initCrypto() with initRustCrypto(); the legacy crypto stack
  was removed upstream in v37.
- Add src/matrix-crypto-store.js: the Rust crypto store requires
  IndexedDB, absent in Node.js, so it is backed by fake-indexeddb and
  snapshotted to disk (rust-crypto-store.v8) to survive restarts.
- Migrate existing libolm crypto state into the Rust store on first run,
  and discard the stored crypto state when the device ID changes.

Homeserver discovery
- Resolve the homeserver via .well-known, so a delegating domain
  (e.g. example.org) works as the configured server URL.

Cross-signing & secure backup
- Add a secured /matrix-chat/secure-backup admin endpoint and a modal
  dialog on the server config node: check status, unlock an existing
  secure backup with its recovery key, or reset and create a new one.

Device verification (new nodes)
- matrix-verification: event source emitting verification requests and
  phase changes, with on-node filters (phase, initiated by, type,
  self-verification, user allowlist, room).
- matrix-verification-action: request, accept, start SAS, confirm,
  mismatch, or cancel an in-flight verification.

Authenticated media
- matrix-receive and matrix-crypt-file use the authenticated media
  endpoints, send a bearer token via msg.headers, and fall back between
  the v3 and v1 media endpoints on a 404.

Fixes
- Surface connection/auth errors in the log; node.error() calls were
  passed an empty msg object, which routed the error and suppressed
  console logging.
- matrix-get-user: await getProfileInfo()/getPresence().
- matrix-invite-room: pass the reason as the third invite() argument
  (the removed callback parameter was shifting it out).
- Guard the verification handlers so a throwing SDK getter cannot crash
  Node-RED.

Docs
- Add the device-verification example flow; update the READMEs and node
  help, correcting stale claims that device verification, secure backup,
  and encrypted file uploads were unsupported.

README.md

@@ -11,13 +11,13 @@ Join our public Matrix room for help: [#node-red-contrib-matrix-chat:skylar.tech
 
 Supported functionality in this package includes:
 
-- **End-to-end encryption (E2EE)**
-  - [Work in progress](#end-to-end-encryption-notes)
-  - Alternative: Use [Pantalaimon](https://github.com/matrix-org/pantalaimon) for E2EE key synchronization across sessions
+- **End-to-end encryption (E2EE)** — send and receive encrypted messages (see the [encryption notes](#end-to-end-encryption-notes))
+- **Cross-signing & secure backup** — interactive setup from the server config node so the bot's own device shows as verified
+- **Device verification** — flow-driven SAS (emoji) verification via the `matrix-verification` and `matrix-verification-action` nodes
 - **Receive events** from rooms: Messages, reactions, images, audio, locations, files, encrypted or unencrypted
 - **Fetch/modify room state**: Update room settings
 - **Paginate room history**
-- **Send files** (encryption support for files coming soon)
+- **Send files** to rooms, encrypted or unencrypted
 - **Send/edit messages** (supports plain text and HTML formats)
 - **Send typing notifications**
 - **Delete events** (messages, reactions, etc.)
@@ -33,6 +33,8 @@ These features allow you to easily build bots, set up chat relays, or even admin
 
 ### Installing
 
+**Requires Node.js 22 or newer** (this is a requirement of the bundled `matrix-js-sdk`).
+
 Install through Node-RED's UI by searching for `node-red-contrib-matrix-chat`, or use the following command inside your Node-RED directory:
 
 ```bash
@@ -51,11 +53,12 @@ You're not limited to just the nodes we've created. Enable global access in your
 
 ### End-to-End Encryption Notes
 
-- This module doesn't handle encryption key synchronization between devices. It’s recommended to use the bot exclusively in Node-RED to prevent issues with E2EE messages.
-- **Storage:** Keys for E2EE are saved in a folder called `matrix-client-storage` within your Node-RED directory. Back up this folder regularly! If lost, you won’t be able to decrypt messages from E2EE rooms.
+- E2EE uses the Rust crypto stack from `matrix-js-sdk`. The first time a bot starts after upgrading from an older version, any existing (legacy libolm) crypto state is migrated automatically.
+- **Storage:** E2EE state is saved in a folder called `matrix-client-storage` within your Node-RED directory. Each account's Rust crypto store is persisted there as `rust-crypto-store.v8` (snapshotted on shutdown and every 5 minutes). Back up this folder regularly! If lost, you won’t be able to decrypt messages from E2EE rooms.
 - To move your bot to a different installation, migrate this folder and ensure the old and new clients don't run simultaneously.
-
-Interested in helping? Contributions to finalize E2EE support are welcome!
+- It’s simplest to dedicate the account to the bot and run it only within Node-RED. The account can also be signed in elsewhere — if so, verify those sessions against the bot (see below) so they trust each other and share keys.
+- **Cross-signing & secure backup:** open the server config node and use the **Set up secure backup & cross-signing** button. It checks the account and lets you unlock an existing secure backup with its recovery key, or create a fresh one — after which the bot's own device is cross-signed and shows as verified to others.
+- **Device verification:** the `matrix-verification` node emits verification requests and phase changes, and `matrix-verification-action` accepts, starts, confirms, or cancels them — so you can build your own approval flow (e.g. emailing the SAS emoji for a human to confirm). See the [device verification example](https://github.com/Skylar-Tech/node-red-contrib-matrix-chat/tree/master/examples#device-verification).
 
 ### Registering a User