fix(web): resolve zodResolver type mismatch for optional description fields

Remove .default('') from zod schemas to align input/output types,
preventing type conflict between zodResolver and useForm in
@hookform/resolvers v5. Use nullish coalescing at entity assignment
sites to ensure string type safety.

web/src/app/home/bots/components/bot-form/BotForm.tsx

@@ -53,7 +53,7 @@ import { CustomApiError } from '@/app/infra/entities/common';
 const getFormSchema = (t: (key: string) => string) =>
   z.object({
     name: z.string().min(1, { message: t('bots.botNameRequired') }),
-    description: z.string().optional().default(''),
+    description: z.string().optional(),
     adapter: z.string().min(1, { message: t('bots.adapterRequired') }),
     adapter_config: z.record(z.string(), z.any()),
     enable: z.boolean().optional(),
@@ -337,7 +337,7 @@ export default function BotForm({
       const updateBot: Bot = {
         uuid: initBotId,
         name: form.getValues().name,
-        description: form.getValues().description,
+        description: form.getValues().description ?? '',
         adapter: form.getValues().adapter,
         adapter_config: form.getValues().adapter_config,
         enable: form.getValues().enable,
@@ -360,7 +360,7 @@ export default function BotForm({
     } else {
       const newBot: Bot = {
         name: form.getValues().name,
-        description: form.getValues().description,
+        description: form.getValues().description ?? '',
         adapter: form.getValues().adapter,
         adapter_config: form.getValues().adapter_config,
       };

web/src/app/home/knowledge/components/kb-form/KBForm.tsx

@@ -46,7 +46,7 @@ import { UUID } from 'uuidjs';
 const getFormSchema = (t: (key: string) => string) =>
   z.object({
     name: z.string().min(1, { message: t('knowledge.kbNameRequired') }),
-    description: z.string().optional().default(''),
+    description: z.string().optional(),
     emoji: z.string().optional(),
     ragEngineId: z
       .string()
@@ -238,7 +238,7 @@ export default function KBForm({
   const onSubmit = (data: z.infer<typeof formSchema>) => {
     const kbData: KnowledgeBase = {
       name: data.name,
-      description: data.description,
+      description: data.description ?? '',
       emoji: data.emoji,
       knowledge_engine_plugin_id: selectedEngineId,
       creation_settings: configSettings,

web/src/app/home/pipelines/components/pipeline-form/PipelineFormComponent.tsx

@@ -80,7 +80,7 @@ export default function PipelineFormComponent({
     ? z.object({
         basic: z.object({
           name: z.string().min(1, { message: t('pipelines.nameRequired') }),
-          description: z.string().optional().default(''),
+          description: z.string().optional(),
           emoji: z.string().optional(),
         }),
         ai: z.record(z.string(), z.any()),
@@ -91,7 +91,7 @@ export default function PipelineFormComponent({
     : z.object({
         basic: z.object({
           name: z.string().min(1, { message: t('pipelines.nameRequired') }),
-          description: z.string().optional().default(''),
+          description: z.string().optional(),
           emoji: z.string().optional(),
         }),
         ai: z.record(z.string(), z.any()).optional(),
@@ -253,7 +253,7 @@ export default function PipelineFormComponent({
   function handleCreate(values: FormValues) {
     const pipeline: Pipeline = {
       config: {},
-      description: values.basic.description,
+      description: values.basic.description ?? '',
       name: values.basic.name,
       emoji: values.basic.emoji,
     };
@@ -280,7 +280,7 @@ export default function PipelineFormComponent({
     const pipeline: Pipeline = {
       config: realConfig,
       // created_at: '',
-      description: values.basic.description,
+      description: values.basic.description ?? '',
       // for_version: '',
       name: values.basic.name,
       emoji: values.basic.emoji,