fix(fips,federation,ui): mesh content browse, removed-node tombstones, modal sizing

FIPS peer content browse over the mesh was failing with "Peer returned
error: 404 Not Found" and never falling back to Tor. `is_peer_allowed_path`
only allowed `/content/<id>` (item fetches) — the catalog endpoint is
exactly `/content` (no trailing slash), so it 404'd over the FIPS peer
listener. A FIPS 404 was also treated as a successful response, so the dial
never retried Tor. Fixes: allow `/content` over the mesh; add
`fips_should_fall_back()` so a FIPS 404/5xx in Auto mode falls back to Tor
(handles version-skew peers reaching a different route). Also correct the
reconnect hint text — the public anchor is TCP/8443, not UDP/8668.

Federation: deleted nodes reappeared because transitive discovery
(`merge` of a peer's advertised trusted peers) re-added any unknown DID.
Add a tombstone store (`removed-nodes.json`): remove_node tombstones the
DID, transitive merge skips tombstoned DIDs, and a remote-triggered
peer-joined is ignored for a removed DID. Explicit local re-add (add_node)
clears the tombstone.

UI: the app credentials modal panel stretched edge-to-edge (height:100%,
max-width:none, items-stretch overlay). Constrain it to a centered card
(max-width 34rem, rounded, dimmed full-screen backdrop) matching the
AppIconGrid / wallet-receive modal.

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

core/archipelago/src/federation/mod.rs

@@ -14,8 +14,8 @@ mod types;
 pub use invites::{accept_invite, create_invite};
 #[allow(unused_imports)]
 pub use storage::{
-    add_node, fips_npub_for_onion, load_nodes, record_peer_transport, remove_node, save_nodes,
-    set_trust_level, update_node,
+    add_node, fips_npub_for_onion, load_nodes, load_removed_dids, record_peer_transport,
+    remove_node, save_nodes, set_trust_level, update_node,
 };
 pub use sync::{build_local_state, deploy_to_peer, sync_with_peer, sync_with_peer_by_did};
 pub use types::{AppStatus, FederatedNode, NodeStateSnapshot, TrustLevel};