feat: redirect from data script

[pratikb64]

Redirect visitors to a URL from a Data Script

What

Adds the ability to redirect a page visitor to any URL from within a page Data Script.

# example
redirect("/login")          # 302 by default
redirect("/login", 301)   # optional custom status code

Why

Data scripts already run server-side on every render and can branch on the
session/user, but there was no way to send the visitor elsewhere. This closes that gap with a one-line helper.

How

• Injects a redirect(location, http_status_code=302) helper into the page
  data script namespace. When called during an actual page render it sets
  frappe.local.flags.redirect_location and raises frappe.Redirect, which the
  Frappe website renderer turns into a real HTTP redirect — entirely
  server-side

Security

• get_page_data is split into a whitelisted wrapper (always
  for_render=False) and an internal _get_page_data(for_render=True) used
  only by the render path — so a client cannot trigger the redirect via the API.
• Pages with a page_data_script are now marked no_cache. A data script can
  branch on the user/session, so without this a render for one user could be
  cached and served to another, bypassing a conditional redirect (auth-bypass).
• Redirect targets come from author-written server-side Python (same trust
  level as any data script); external URLs are intentionally allowed.

Tests

• test_redirect_from_page_data_script: asserts the rendered response is a
  302 to the target URL, and that the editor's get_page_data() call is a
  no-op returning empty data.

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.63%. Comparing base (7f03261) to head (a63b47f).
⚠️ Report is 1 commits behind head on develop.
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Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #619      +/-   ##
===========================================
+ Coverage    58.41%   58.63%   +0.21%     
===========================================
  Files           29       29              
  Lines         3239     3256      +17     
===========================================
+ Hits          1892     1909      +17     
  Misses        1347     1347              

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[surajshetty3416]

@pratikb64 Update docs as well?

https://docs.frappe.io/builder/data-script