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>

core/archipelago/src/mesh/mod.rs

@@ -99,7 +99,17 @@ pub(crate) async fn seed_federation_peers_into_mesh(
         Ok(n) => n,
         Err(_) => return,
     };
+    // Skip nodes whose onion we've already seeded: the same physical node can
+    // linger in the federation list under two dids (see B1/B2). Seeding both
+    // would create two chat contacts for one node — one by name+logo and one
+    // by raw did. One onion → one mesh contact.
+    let mut seen_onions = std::collections::HashSet::new();
     for node in nodes {
+        let onion_key = node.onion.trim_end_matches(".onion").to_string();
+        if !onion_key.is_empty() && !seen_onions.insert(onion_key) {
+            tracing::debug!(did = %node.did, onion = %node.onion, "skipping duplicate federation node (onion already seeded)");
+            continue;
+        }
         upsert_federation_peer(state, &node.pubkey, &node.did, node.name.as_deref()).await;
     }
 }