feat: harden support, localize knowledge and add operator availability [skip ci]

Source-only publication of reviewed commit 64e96a7f423673dc29ad56485be9fc79bce8af1c.

Passed in isolation: focused frontend/backend tests, race checks, TypeScript typecheck, lint, Go compilation, Flowgram build, and deterministic SDK build/tests.

Not accepted as a production release: Next.js export/native assembly remains blocked by environment memory limits; browser interaction and MySQL staging acceptance remain unverified. No production server, database/schema, runtime configuration, deployment, release tag, or workflow execution was performed.

Expected source tree: 0a4a7528e9.

internal/repositories/conversation_dispatch_queries.go

@@ -0,0 +1,17 @@
+package repositories
+
+import (
+	"agent-desk/internal/models"
+	"agent-desk/internal/pkg/enums"
+
+	"gorm.io/gorm"
+)
+
+// FindPendingDispatchBatch returns a bounded, checked page. A failed read must
+// not be mistaken for an empty queue by setup or the periodic dispatcher.
+func (r *conversationRepository) FindPendingDispatchBatch(db *gorm.DB, limit int) ([]models.Conversation, error) {
+	conversations := make([]models.Conversation, 0)
+	err := db.Where("status = ? AND current_assignee_id = ?", enums.IMConversationStatusPending, 0).
+		Order("id DESC").Limit(limit).Find(&conversations).Error
+	return conversations, err
+}