fix(frontend): Add comprehensive debug logging for Epic creation

Add detailed console logging to diagnose Epic creation issue where
no request is being sent to backend.

Changes:
- Add form submission event logging in epic-form.tsx
- Add API request/response logging in epicsApi.create
- Add HTTP client interceptor logging for all requests/responses
- Log authentication status, payload, and error details
- Log form validation state and errors

This will help identify:
- Whether form submit event fires
- Whether validation passes
- Whether API call is triggered
- Whether authentication token exists
- What errors occur (if any)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

components/epics/epic-form.tsx

@@ -71,8 +71,11 @@ export function EpicForm({ projectId, epic, onSuccess, onCancel }: EpicFormProps
   });
 
   async function onSubmit(data: EpicFormValues) {
+    console.log('[EpicForm] onSubmit triggered', { data, user: user?.id, projectId });
+
     try {
       if (!user?.id) {
+        console.error('[EpicForm] User not authenticated');
         toast.error('User not authenticated');
         return;
       }
@@ -82,20 +85,29 @@ export function EpicForm({ projectId, epic, onSuccess, onCancel }: EpicFormProps
         estimatedHours: data.estimatedHours || undefined,
       };
 
+      console.log('[EpicForm] Prepared payload', payload);
+
       if (isEditing) {
+        console.log('[EpicForm] Updating epic', { epicId: epic.id });
         await updateEpic.mutateAsync({
           id: epic.id,
           data: payload,
         });
+        console.log('[EpicForm] Epic updated successfully');
       } else {
-        await createEpic.mutateAsync({
+        console.log('[EpicForm] Creating epic', { projectId, createdBy: user.id });
+        const result = await createEpic.mutateAsync({
           projectId,
           createdBy: user.id,
           ...payload,
         });
+        console.log('[EpicForm] Epic created successfully', result);
       }
+
+      console.log('[EpicForm] Calling onSuccess callback');
       onSuccess?.();
     } catch (error) {
+      console.error('[EpicForm] Operation failed', error);
       const message = error instanceof Error ? error.message : 'Operation failed';
       toast.error(message);
     }
@@ -112,7 +124,16 @@ export function EpicForm({ projectId, epic, onSuccess, onCancel }: EpicFormProps
 
   return (
     <Form {...form}>
-      <form onSubmit={form.handleSubmit(onSubmit)} className="space-y-6">
+      <form
+        onSubmit={(e) => {
+          console.log('[EpicForm] Form submit event triggered', {
+            formState: form.formState,
+            values: form.getValues(),
+            errors: form.formState.errors,
+          });
+          form.handleSubmit(onSubmit)(e);
+        }}
+        className="space-y-6">
         <FormField
           control={form.control}
           name="name"