Consume NIP-19 relay hints for event fetching

Extract and use relay hints from bech32 entities (nevent, nprofile, naddr)
and event tag references (e, q tags) to fetch events from hinted relays
not in the user's relay pool.

Changes:
- Parse relay hints from bech32 TLV data in URLHandler
- Pass relay hints through SearchType and NoteReference enums
- Add ensureConnected() to RelayPool for ephemeral relay connections
- Implement ephemeral relay lease management with race condition protection
- Add repostTarget() helper to extract relay hints from repost e tags
- Add QuoteRef struct to preserve relay hints from q tags (NIP-10/NIP-18)
- Support relay hints in replies with author pubkey in e-tags (NIP-10)
- Implement fallback broadcast when hinted relays don't respond
- Add comprehensive test coverage for relay hint functionality
- Add DEBUG logging for relay hint tracing during development

Implementation details:
- Connect to hinted relays as ephemeral, returning early when first connects
- Use total deadline to prevent timeout accumulation across hint attempts
- Decrement lease count before suspension points to ensure atomicity
- Fall back to broadcast if hints don't resolve or respond

Closes: https://github.com/damus-io/damus/issues/1147
Changelog-Added: Added relay hint support for nevent, nprofile, naddr links and event tag references (reposts, quotes, replies)
Signed-off-by: alltheseas
Signed-off-by: Daniel D'Aquino <daniel@daquino.me>
Co-authored-by: alltheseas <alltheseas@users.noreply.github.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Daniel D'Aquino <daniel@daquino.me

nostrdb/NdbNote.swift

@@ -435,6 +435,10 @@ extension NdbNote {
         References<QuoteId>(tags: self.tags)
     }
 
+    public var referenced_quote_refs: References<QuoteRef> {
+        References<QuoteRef>(tags: self.tags)
+    }
+
     public var referenced_noterefs: References<NoteRef> {
         References<NoteRef>(tags: self.tags)
     }
@@ -539,6 +543,14 @@ extension NdbNote {
         return thread_reply()?.reply.note_id
     }
 
+    /// Returns the direct reply reference with relay hint if available.
+    ///
+    /// Per NIP-10, the reply `e` tag may include a relay URL at position 2 where
+    /// the replied-to event can be found.
+    public func direct_reply_ref() -> NoteRef? {
+        return thread_reply()?.reply
+    }
+
     // NDBTODO: just use Id
     public func thread_id() -> NoteId {
         guard let root = self.thread_reply()?.root else {