Add manage layers interface with proper permalink and CSS variables

[Copilot]

The manage layers functionality existed only as a component at /components/manage-layers/index.html without a proper interface structure or permalink, preventing integration with TPEN's navigation system.

Changes

New Interface

• Created /interfaces/manage-layers/ with permalink /project/manage/layers
• Uses tpen-page wrapper and tpen-card components following established patterns
• Includes explanatory guide component for user guidance

Style Refactor

• Replaced hardcoded colors in manage-layers and manage-pages components with CSS variables:
  • #007bff → var(--interface-primary)
  • #dc3545 → var(--error-color)
  • #28a745 → var(--success-color)
  • #ffc107 → var(--warning-color)
• Used filter: brightness(0.85) for hover states instead of additional hardcoded values

Navigation

• Updated manage-project interface link from component path to new permalink

<!-- Before -->
<a href="/components/manage-layers/index.html?projectID=${projectID}">

<!-- After -->
<a href="/project/manage/layers?projectID=${projectID}">

All existing functionality preserved.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Manage Layers and Pages Interface</issue_title>
<issue_description>There is not an interface to manage project layers and pages, which is core functionality for setting up a Project and transcription. It needs an actual interface and permalink. See /components/manage-layers/index.html for what is currently available.</issue_description>

<agent_instructions>use the tpen page wrapper and follow the patterns in the other interfaces. Use main.css variables where possible instead of inline colors and such.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Manage Layers and Pages Interface #354

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[cubap]

Approving with a suggestion for portability: inside components/manage-layers/index.html, consider changing <script src="/components/explanatory-guide/fixedGuideComponent.js" type="module"></script> to a relative path <script src="../explanatory-guide/fixedGuideComponent.js" type="module"></script> to ensure it works if the app is deployed in a subdirectory. (Gemini)