text: Title: Tabulator : tooltips
  Body: Hello all,
  
  #### ALL software version info
  MacOs with Chrome, Safari or FireFox  
  bokeh 3.6.1 and panel >= 1.5.2
  
  #### Description of expected behavior and the observed behavior
  
  The issue occurs in Tabulator when using `header_tooltips` with a `FastListTemplate`. The background and font colors of the tooltips are both dark, making the text unreadable.
  
  I couldn't find the CSS responsible for the background color.
  
  #### Complete, minimal, self-contained example code that reproduces the issue
  
  ```python
  import pandas as pd
  import panel as pn
  import random
  import numpy as np
  
  pn.extension('tabulator')
  
  n = 100
  data = {
      "ID": range(1, n + 1),  
      "Name": [f"Name_{i}" for i in range(1, n + 1)],  
      "Age": [random.randint(18, 70) for _ in range(n)],  
      "Score": [round(random.uniform(50, 100), 2) for _ in range(n)], 
      "Category": [random.choice(["A", "B", "C"]) for _ in range(n)], 
      "Active": [random.choice([True, False]) for _ in range(n)], 
      "Date": pd.date_range("2023-01-01", periods=n), 
      "Comment": [f"Comment_{i}" for i in range(1, n + 1)], 
      "Rating": [round(random.uniform(1, 5), 1) for _ in range(n)], 
      "Value": np.random.randint(100, 500, size=n)}
  df = pd.DataFrame(data)
  
  htt = {x: x for x in data.keys()}
  
  tabulator = pn.widgets.Tabulator(df, page_size=10, sizing_mode='stretch_width', header_tooltips=htt)
  # app = tabulator  # OK
  
  template = pn.template.FastListTemplate(title="Tabulator test", main=[tabulator])  # bug 
  
  # template = pn.template.BootstrapTemplate(title="Tabulator test", main=[tabulator])  # OK
  # template = pn.template.MaterialTemplate(title="Tabulator test", main=[tabulator])  # OK
  # template = pn.template.MaterialTemplate(title="Tabulator test", main=[tabulator])  # OK
  
  app = template
  
  app.servable()  
  app.show() 
  
  ```
  
  #### Screenshots or screencasts of the bug in action
  
  <img width="770" alt="Image" src="https://github.com/user-attachments/assets/76b5606e-03cc-4505-85b6-ef379496675a" />
  