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.

examples/README.md

@@ -431,6 +431,27 @@ Downloads received files/images. If the file is encrypted, it will decrypt it fo
 
 </details>
 
+### Device Verification
+
+<details>
+<summary>Handle device verification (SAS / emoji)</summary>
+
+[View JSON](device-verification-flow.json)
+
+An end-to-end example of interactive device verification. The `matrix-verification` node emits every verification request and phase change; the flow routes by phase, automatically **accepts** incoming requests and **starts SAS**, then surfaces the SAS emoji so a human can compare it. Inject nodes let you **confirm** or **reject** the match, and there are paths to have the bot **request** verification of a specific user's device, or a user in a room.
+
+Requires end-to-end encryption to be enabled on the server config node. For the bot's own device to be trusted by others, also set up cross-signing via the **Set up secure backup & cross-signing** button on the server config node.
+
+**Instructions:**
+
+1. Import the flow and set the Matrix server config on each matrix node.
+2. Replace the `@CHANGE_ME:example.org` / `CHANGE_ME` placeholders in the "Verify a user" inject nodes if you want to use the bot-initiated paths.
+3. To verify the bot from another client, start a verification with it, watch the debug sidebar for the `sas` event, compare the emoji, then click the **Confirm SAS match** inject.
+
+![device-verification-flow.png](device-verification-flow.png)
+
+</details>
+
 ### Deprecated
 
 <details>