Add defaultStyling.json support for persistent per-type vertex and edge styling

[jkemmererupgrade]

Description

Add support for a defaultStyling.json file that provides persistent per-type vertex and edge styling defaults. When mounted into the Docker container, the file's values are merged into the user styling
store on startup, giving teams a consistent visual baseline across non-persistent browser sessions (e.g., AWS WorkSpaces Web).

Key capabilities:

• Docker mount: Place a defaultStyling.json at the configuration folder path to auto-apply styling on load
• Lucide icon support: Reference icons by name (e.g., "icon": "user") — resolved to SVG data URIs at runtime
• Import / Export / Reset UI: New controls in Settings to import a styling file, export current styling, and reset all styling to defaults
• Per-type Reset to Default: Each node/edge type's style dialog has a "Reset to Default" button that restores the mounted file's values
• Zod validation: Strict schema validation with clear error logging for malformed files

Validation

• All 1365 tests pass (pnpm test)
• pnpm checks passes (lint, format, types)
• Docker tested with mounted defaultStyling.json — styling applied on startup, import/export/reset all functional
• Incognito window testing confirmed clean-state behavior
• New unit tests cover: Zod parsing, icon resolution, import/export hooks, merge logic, configuration integration

Related Issues

Addresses #1265, #112, #173, #573, #689

Check List

• I confirm that my contribution is made under the terms of the Apache 2.0 license.
• I have run pnpm checks to ensure code compiles and meets standards.
• I have run pnpm test to check if all tests are passing.
• I have covered new added functionality with unit tests if necessary.
• I have added an entry in the Changelog.md.

[jkemmererupgrade]

I also have a follow-on PR that will add a picker to the vertex/edge to filter and select one of the lucide icons. merged it as a commit to this PR. This is ready for review @kmcginnes.

[jkemmererupgrade]

A note on the Lucide Licensing:
https://lucide.dev/license

Lucide uses the ISC License — one of the most permissive open-source licenses. It allows:

  - Use in commercial and open-source projects
  - Bundling and distribution
  - Modification
  - Any purpose, with or without fee

  The only requirement is keeping the copyright notice in distributed copies. Graph Explorer already ships lucide-react as a dependency (package.json line 43), so the license is already included in node_modules. 

[kmcginnes]

@jkemmererupgrade thanks for the submission, and I apologize for the slow response.

This looks like a great set of features, and they are ones I've been really wanting for myself as a user.

I won't have a chance to dive in to the details until next week at the earliest. Let me know if that works for you.

[jkemmererupgrade]

@jkemmererupgrade thanks for the submission, and I apologize for the slow response.

This looks like a great set of features, and they are ones I've been really wanting for myself as a user.

I won't have a chance to dive in to the details until next week at the earliest. Let me know if that works for you.

Thank you @kmcginnes! Next week is great. Please let me know what else I can do to assist.