fix(federation,cloud): dedup trusted nodes + chat contacts by onion; guard cloud my-folders (B1,B2,B4)

B1/B2: the same physical node can linger in the federation list under two
dids (e.g. after a did/key change). An onion is a node's unique stable
identity, so two entries with the same onion are one node. This showed the
node twice in the trusted-node list (B1) and as two mesh chat contacts —
one by name+logo, one by raw did (B2).
- storage::load_nodes now collapses same-onion entries (keep first, merge
  fips_npub/name/last_state) so every consumer (list + chat seed + sync)
  sees one entry per node.
- federation::sync merge_transitive_peers also matches by onion (not just
  did) so new transitive hints don't re-add a known node under a new did.
- mesh::seed_federation_peers_into_mesh skips already-seeded onions (belt
  and suspenders).
- Unit tests for dedup_nodes_by_onion (collapse + onion-suffix handling).

B4: filebrowser-client.listDirectory only checked res.ok before res.json(),
so when File Browser is absent (nginx serves the SPA index.html, 200) or
down (502) the JSON parse threw the opaque "Unexpected token '<'". Now it
checks the content-type and throws a friendly "File Browser is not
available" the Cloud view already renders as an empty state.

Verified: dedup unit tests 2/2; live .198 (15 entries→13 distinct onions)
restarted healthy on new binary; B4 guard present in built bundle + deployed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

neode-ui/src/api/filebrowser-client.ts

@@ -102,7 +102,15 @@ class FileBrowserClient {
     const res = await fetch(`${this.baseUrl}/api/resources${safePath}`, {
       headers: this.headers(),
     })
-    if (!res.ok) throw new Error(`Failed to list directory: ${res.status}`)
+    if (!res.ok) throw new Error(`File Browser is not available (HTTP ${res.status})`)
+    // When File Browser isn't installed, nginx falls through to the SPA and
+    // returns index.html (200, text/html); when it's down it returns 502.
+    // Either way res.json() would throw the opaque "Unexpected token '<'"
+    // error, so detect a non-JSON body and surface a friendly message instead.
+    const contentType = res.headers.get('content-type') || ''
+    if (!contentType.includes('application/json')) {
+      throw new Error('File Browser is not available — install or start the File Browser app to use your folders')
+    }
     const data: FileBrowserListResponse = await res.json()
     return (data.items || []).map((item) => ({
       ...item,