feat(gateway): persist chat sessions and messages in PostgreSQL

- store: new chat_sessions/chat_messages tables with CRUD, ILIKE message
  search, and auto-titling from the first user message
- context: optional Persister on the sliding-window store — messages are
  saved asynchronously on Add, sessions not in memory are restored from
  the database on Get
- orchestrator: ProcessInput/FinishRound now carry userID so persisted
  messages have an owner
- api: real session handlers (list/create/delete), message history and
  clear endpoints, working message search and three-format export
  (markdown/txt/json), fixing the short-ID panic in export
- main: migration, store wiring, ctxStore persister adapter

Tests: chat store handler lifecycle (fake store), context persister
save/restore, stub auth login flow updated.

backend/cmd/cyrene/main.go

@@ -37,10 +37,12 @@ import (
 	tracepkg "git.yeij.top/AskaEth/Cyrene_v2/services/ai-core/trace"
 	perfpkg "git.yeij.top/AskaEth/Cyrene_v2/services/ai-core/perf"
 	aiCoreCtx "git.yeij.top/AskaEth/Cyrene_v2/services/ai-core/context"
+	"git.yeij.top/AskaEth/Cyrene_v2/services/ai-core/model"
 	"git.yeij.top/AskaEth/Cyrene_v2/services/ai-core/orchestrator"
 	"git.yeij.top/AskaEth/Cyrene_v2/services/ai-core/persona"
 	"git.yeij.top/AskaEth/Cyrene_v2/services/ai-core/subsession"
 	"git.yeij.top/AskaEth/Cyrene_v2/services/gateway/api"
+	"git.yeij.top/AskaEth/Cyrene_v2/services/gateway/store"
 	"git.yeij.top/AskaEth/Cyrene_v2/services/gateway/ws"
 	"git.yeij.top/AskaEth/Cyrene_v2/services/memory"
 	bridge "git.yeij.top/AskaEth/Cyrene_v2/services/platform-bridge"
@@ -79,6 +81,7 @@ func main() {
 	} else {
 		defer database.Close()
 		db.RunMigration(context.Background(), database, "memories", db.SplitSQL(memory.CreateTableSQL()))
+		db.RunMigration(context.Background(), database, "chat", db.SplitSQL(store.CreateTableSQL()))
 	}
 
 	// === 3. NATS (in-process) ===
@@ -161,6 +164,14 @@ func main() {
 	ctxStore := aiCoreCtx.NewStore(4000, 50)
 	logger.Infof("[context] sliding window ready (4000 tokens, 50 turns)")
 
+	// === 9.5 Chat persistence (sessions + messages) ===
+	var chatStore *store.ChatStore
+	if database != nil {
+		chatStore = store.NewChatStore(database)
+		ctxStore.SetPersister(&chatPersisterAdapter{s: chatStore})
+		logger.Infof("[chat] session/message persistence ready")
+	}
+
 	// === 10. AI-Core: Sub-session Manager ===
 	subMgr := subsession.NewManager(
 		&subsession.GeneralProvider{},
@@ -238,6 +249,9 @@ func main() {
 	if memSvc != nil {
 		gwDeps.MemorySvc = memory.NewAPIAdapter(memSvc)
 	}
+	if chatStore != nil {
+		gwDeps.ChatStore = chatStore
+	}
 	gwDeps.VoiceSvc = voiceSvc
 
 	wsHub := ws.NewHub(orch)
@@ -331,6 +345,31 @@ func (a *perfAdapter) History() []map[string]any {
 	return result
 }
 
+// chatPersisterAdapter adapts store.ChatStore to aiCoreCtx.Persister.
+type chatPersisterAdapter struct{ s *store.ChatStore }
+
+func (a *chatPersisterAdapter) SaveMessage(sessionID, userID string, msg model.Message) {
+	if userID == "" {
+		userID = "unknown"
+	}
+	if err := a.s.AddMessage(context.Background(), sessionID, userID, msg.Role, msg.Content); err != nil {
+		logger.Infof("[chat] persist message failed: %v", err)
+	}
+}
+
+func (a *chatPersisterAdapter) LoadRecent(sessionID string, limit int) []model.Message {
+	msgs, err := a.s.ListMessages(context.Background(), sessionID, limit)
+	if err != nil {
+		logger.Infof("[chat] load history failed: %v", err)
+		return nil
+	}
+	out := make([]model.Message, len(msgs))
+	for i, m := range msgs {
+		out[i] = model.Message{SessionID: m.SessionID, Role: m.Role, Content: m.Content, CreatedAt: m.CreatedAt}
+	}
+	return out
+}
+
 // toolExecAdapter adapts the plugin registry to orchestrator.ToolExecutor.
 type toolExecAdapter struct{ reg *plugin.Registry }
 
@@ -389,7 +428,7 @@ func loadAdaptersFromConfig(router *bridge.Router, cfg *bridge.BridgeConfig, orc
 
 	router.SetMessageHandler(func(msg *bridge.UnifiedMessage) {
 		sessionID := "bridge-" + msg.Source
-		tokenCh, _, err := orch.ProcessInput(context.Background(), sessionID, msg.Content)
+		tokenCh, _, err := orch.ProcessInput(context.Background(), sessionID, msg.SenderID, msg.Content)
 		if err != nil { return }
 		var fc string
 		for t := range tokenCh { fc += t.Content }