feat(settings): per-service FIPS/Tor transport preference

Adds a user-configurable toggle for how each peer-to-peer service
reaches federated peers. Three options per service:

- Auto (default) — FIPS preferred, Tor fallback (current behavior).
- FIPS only — fail rather than fall through to Tor.
- Tor only — explicit opt-in to onion anonymity for that service.

Services covered (matching the UI rows):
- Federation — state sync, invites, peer notifications
- Peers — address/DID rotation broadcasts
- Peer Files — content catalog download/browse/preview
- Messaging — archipelago channel + mesh bridge
- Mesh File Sharing — content_ref blob fetches

Implementation:
- settings::transport — persisted struct + process-wide OnceLock handle
  (so deep call sites don't need data_dir threaded through signatures).
  On-disk file: <data_dir>/settings/transport_preferences.json; missing
  or corrupt → defaults (Auto everywhere).
- settings::transport::init() called from main.rs after config load.
- fips::dial::PeerRequest gains a .service(kind) builder; send_* checks
  the preference before choosing a transport. FIPS-only fails loudly
  when FIPS is unavailable (so users who pick it know when something
  falls back).
- Every FIPS-first migration site tags its PeerRequest with the
  matching PeerService so the toggle actually applies.
- transport.preferences + transport.set-preference RPCs added; wired
  into the dispatcher.
- neode-ui/src/views/settings/TransportPrefsCard.vue — standalone card
  with a 5-row Auto/FIPS/Tor tri-state. Not wired into Settings.vue —
  the user places components themselves (see feedback_ui_entry_points).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

core/archipelago/src/network/dwn_sync.rs

@@ -184,6 +184,7 @@ async fn sync_single_peer(
 
     // Step 1: Check peer health
     let (health_resp, _) = PeerRequest::new(fips_npub, onion, "/dwn/health")
+        .service(crate::settings::transport::PeerService::Federation)
         .timeout(std::time::Duration::from_secs(30))
         .send_get()
         .await
@@ -208,6 +209,7 @@ async fn sync_single_peer(
     });
 
     let (pull_res, _) = PeerRequest::new(fips_npub, onion, "/dwn")
+        .service(crate::settings::transport::PeerService::Federation)
         .timeout(std::time::Duration::from_secs(30))
         .send_json(&pull_body)
         .await
@@ -265,6 +267,7 @@ async fn sync_single_peer(
 
         // Best-effort push — don't fail the whole sync if a batch fails.
         match PeerRequest::new(fips_npub, onion, "/dwn")
+        .service(crate::settings::transport::PeerService::Federation)
             .timeout(std::time::Duration::from_secs(30))
             .send_json(&push_body)
             .await