test: cover page and static PHP controllers

[erseco]

Summary

• extend standalone stubs with initial-state, URL generator, template response, and CSP behavior
• cover SwController response body and Service Worker headers
• cover TemplateController authentication and bundled blank-package streaming
• cover ViewController id/path resolution, missing/denied files, initial state, editor/preview mode, script registration, and CSP
• add these controller files to the backend Clover scope
• retain the 90% backend threshold

Stack

Depends on #120, which depends on #119.

1. test: extend PHP coverage to app and preview #119 — AppInfo + Preview
2. test: cover read-only PHP controllers #120 — read-only controllers
3. this PR — static/page controllers
4. final — EditorController / extracted editor logic

Validation

• CI: green
• Playground preview: green
• backend coverage: 93.99%
• ViewController: 100% lines
• SwController: 85.71% lines
• TemplateController: 86.67% lines

[github-actions]

Preview this PR in the Nextcloud Playground

A fresh Nextcloud boots in your browser with this branch's exelearning app installed and enabled (log in as admin / admin). Two sample .elpx are seeded under exelearning-samples/ in Files — click one to open the viewer.

eXeLearning editor: v4.0.5 (overlaid at boot from the upstream release).

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (test/coverage-read-controllers@2d7ac4b). Learn more about missing BASE report.

Additional details and impacted files

@@                        Coverage Diff                        @@
##             test/coverage-read-controllers     #121   +/-   ##
=================================================================
  Coverage                                  ?   94.93%           
  Complexity                                ?      114           
=================================================================
  Files                                     ?       19           
  Lines                                     ?      513           
  Branches                                  ?       54           
=================================================================
  Hits                                      ?      487           
  Misses                                    ?       19           
  Partials                                  ?        7           

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