feat(acl): redesign ACL with conversation scope selector (#297)

Backend
- New subject kinds: all / channel_identity / channel_type
- Source scope fields on bot_acl_rules: source_channel,
  source_conversation_type, source_conversation_id, source_thread_id
- Fix source_scope_check constraint: resolve source_channel server-side
  (channel_type → subject_channel_type; channel_identity → DB lookup)
- Add GET /bots/:id/acl/channel-types/:type/conversations to list
  observed conversations by platform type
- ListObservedConversations: include private/DM chats, normalise
  conversation_type; COALESCE(name, handle) for display name
- enrichConversationAvatar: persist entry.Name → conversation_name
  (keeps Telegram group titles current on every message)
- Unify Priority type to int32 across Go types to match DB INTEGER;
  remove all int/int32 casts in service layer
- Fix duplicate nil guard in Evaluate; drop dead SourceScope.Channel field
- Migration 0048_acl_redesign

Frontend
- Drag-and-drop rule priority reordering (SortableJS/useSortable);
  fix reorder: compute new order from oldIndex/newIndex directly,
  not from the array (which useSortable syncs after onEnd)
- Conversation scope selector: searchable popover backed by observed
  conversations (by identity or platform type); collapsible manual-ID fallback
- Display: name as primary label, stable channel·type·id always shown
  as subtitle for verification
- bot-terminal: accessibility fix on close-tab button (keyboard events)
- i18n: drag-to-reorder, conversation source, manual IDs (en/zh)

Tests: update fakeChatACL to Evaluate interface; fix SourceScope literals.
SDK/spec regenerated.

internal/db/sqlc/models.go

@@ -37,6 +37,7 @@ type Bot struct {
 	Metadata            []byte             `json:"metadata"`
 	CreatedAt           pgtype.Timestamptz `json:"created_at"`
 	UpdatedAt           pgtype.Timestamptz `json:"updated_at"`
+	AclDefaultEffect    string             `json:"acl_default_effect"`
 }
 
 type BotAclRule struct {
@@ -45,7 +46,6 @@ type BotAclRule struct {
 	Action                 string             `json:"action"`
 	Effect                 string             `json:"effect"`
 	SubjectKind            string             `json:"subject_kind"`
-	UserID                 pgtype.UUID        `json:"user_id"`
 	ChannelIdentityID      pgtype.UUID        `json:"channel_identity_id"`
 	SourceChannel          pgtype.Text        `json:"source_channel"`
 	SourceConversationType pgtype.Text        `json:"source_conversation_type"`
@@ -54,6 +54,10 @@ type BotAclRule struct {
 	CreatedByUserID        pgtype.UUID        `json:"created_by_user_id"`
 	CreatedAt              pgtype.Timestamptz `json:"created_at"`
 	UpdatedAt              pgtype.Timestamptz `json:"updated_at"`
+	Priority               int32              `json:"priority"`
+	Enabled                bool               `json:"enabled"`
+	Description            pgtype.Text        `json:"description"`
+	SubjectChannelType     pgtype.Text        `json:"subject_channel_type"`
 }
 
 type BotChannelConfig struct {