feat(chat): fee floor, real delivery status, pay-from-funded, funds pre-check

Chat sends move 0 value, so the network fee is structurally load-bearing (it's
the only thing that forces a real shielded input; 0-value + 0-fee builds a
degenerate, unrelayable tx). Three gaps addressed:

1. Fee floor — broadcastChatMemos now uses max(getDefaultFee(), kChatMinFeeDrgx),
   so a 0 / too-low global default-fee setting can't silently break chat.

2. Real delivery status — the echo was marked Sent on SUBMIT regardless of the
   on-chain outcome (the z_sendmany callback was empty), so failures were
   invisible and the Retry affordance never fired for async failures. Add a third
   ChatDelivery::Sending state (appended so persisted 0=Sent stays valid); record
   the echo in-memory as Sending, and resolve it to Sent/Failed from the
   z_sendmany completion callback — persisting only the final status (so a restart
   never shows a stuck spinner; a stray persisted Sending loads as Sent). A subtle
   "sending…" label shows while in flight.

3. Pay-from-funded + pre-check — z_sendmany spends from one z-address, and the
   identity reply address may be unfunded while funds sit elsewhere. chatPayFromZaddr
   picks a spendable z-address that can cover the fee (preferring the identity
   address); the memo still advertises the identity address as reply-to, so paying
   from a different note is transport-transparent. If nothing can cover the fee, a
   clear "need a small shielded balance" toast replaces the cryptic failure.

Full node only for the callback path; lite resolves optimistically on queue.
8-language strings + CJK subset (+1 glyph 賄).

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

src/chat/chat_database.cpp

@@ -267,7 +267,10 @@ bool ChatDatabase::deserialize(const std::string& json, ChatMessage& out) const
         out.body = parsed.value("b", std::string());
         out.timestamp = parsed.value("ts", static_cast<std::int64_t>(0));
         out.payload_position = static_cast<std::size_t>(parsed.value("pos", static_cast<std::uint64_t>(0)));
-        out.delivery = static_cast<ChatDelivery>(parsed.value("dl", 0));  // old rows → Sent
+        out.delivery = static_cast<ChatDelivery>(parsed.value("dl", 0));  // old rows → Sent (0)
+        // A persisted "Sending" means we crashed mid-broadcast; the outcome is unknown. Resolve it
+        // optimistically to Sent on load so it can't show a stuck spinner forever.
+        if (out.delivery == ChatDelivery::Sending) out.delivery = ChatDelivery::Sent;
         return true;
     } catch (const std::exception&) {
         return false;

src/chat/chat_message.h

@@ -10,9 +10,11 @@ namespace dragonx::chat {
 
 enum class ChatDirection { Incoming, Outgoing };
 enum class ChatMessageKind { Message, ContactRequest };
-// Outgoing delivery: Sent = the broadcast was submitted; Failed = it wasn't (not connected, no
-// spendable address, a send already in progress). Always Sent for incoming.
-enum class ChatDelivery { Sent, Failed };
+// Outgoing delivery status. Sending = broadcast in flight (async op not yet resolved); Sent = the
+// daemon accepted + broadcast the tx; Failed = it didn't (not connected, no funded address, rejected).
+// Always Sent for incoming. NB: the values are persisted (chat DB serializes the int), so Sent MUST
+// stay 0 and new states are APPENDED — never reordered.
+enum class ChatDelivery { Sent, Failed, Sending };
 
 struct ChatMessage {
     ChatDirection direction = ChatDirection::Incoming;

src/chat/chat_service.cpp

@@ -109,4 +109,15 @@ bool ChatService::recordOutgoing(const ChatMessage& message) {
     return false;
 }
 
+bool ChatService::recordOutgoingPending(const ChatMessage& message) {
+    // In-memory only — deliberately NOT persisted yet, so "Sending" never survives to a restart; the
+    // row is written by resolveOutgoing() once the broadcast resolves to Sent/Failed.
+    return store_.append(message);
+}
+
+void ChatService::resolveOutgoing(const std::string& txid, ChatDelivery delivery) {
+    const ChatMessage* updated = store_.updateDelivery(txid, delivery);
+    if (updated && db_) db_->append(*updated);  // first persist, carrying the final status
+}
+
 } // namespace dragonx::chat

src/chat/chat_service.h

@@ -76,6 +76,12 @@ public:
     // only local record of what we sent.)
     bool recordOutgoing(const ChatMessage& message);
 
+    // Two-phase echo for delivery tracking: record in-memory only (shows immediately as Sending),
+    // then resolveOutgoing() flips the status once the broadcast completes AND persists it with the
+    // final status — so a restart never shows a stuck "Sending".
+    bool recordOutgoingPending(const ChatMessage& message);
+    void resolveOutgoing(const std::string& txid, ChatDelivery delivery);
+
     const ChatStore& store() const { return store_; }
     ChatStore& store() { return store_; }
 

src/chat/chat_store.cpp

@@ -34,6 +34,16 @@ std::vector<ChatMessage> ChatStore::conversation(const std::string& conversation
     return out;
 }
 
+const ChatMessage* ChatStore::updateDelivery(const std::string& txid, ChatDelivery delivery) {
+    for (auto& message : messages_) {
+        if (message.txid == txid) {
+            message.delivery = delivery;
+            return &message;
+        }
+    }
+    return nullptr;
+}
+
 std::vector<std::string> ChatStore::conversationIds() const {
     std::vector<std::string> ids;
     std::unordered_set<std::string> seenIds;

src/chat/chat_store.h

@@ -21,6 +21,10 @@ public:
     // Messages in a conversation, in insertion order.
     std::vector<ChatMessage> conversation(const std::string& conversationId) const;
 
+    // Update an outgoing echo's delivery status by its local txid. Returns a pointer to the updated
+    // message (for the caller to persist), or nullptr if no message has that txid.
+    const ChatMessage* updateDelivery(const std::string& txid, ChatDelivery delivery);
+
     // Distinct conversation ids, in first-seen order.
     std::vector<std::string> conversationIds() const;