Allow Delete key to delete selected nodes and edges

[nivedita9009]

Closes #79

🤔 Section A - Description

What does this PR do?

This PR adds support for the Delete key in addition to the Backspace key for deleting selected nodes and edges in the ReactFlow editor.

Why?

Previously only the Backspace key could delete selected nodes and edges. This change allows users to use either Backspace or Delete, matching common desktop application behavior.

---

✅ Verification

• Ran the application locally.
• Selected a node.
• Pressing Backspace deletes the selected node.
• Pressing Delete also deletes the selected node.
• Existing functionality continues to work.

---

🔎 Quick Self Check

• I tested my changes locally.
• My changes are limited to this feature.
• I did not introduce unrelated changes.
• I followed the project's coding style.

---

📜 BioBuilder Contributor License Agreement

• I confirm that I wrote this code myself and agree to the project's Contributor License Agreement.

[MarkAStevens04]

Hi @nivedita9009!! Thank you SO MUCH for making your first contribution 🎉, we're lucky to have you!! Please make sure you've filled out the pull request template, it'll make reviewing this change a lot easier! Feel free to just attach as a comment to this PR. ❤️

Closes {LINK TO GH ISSUE}

## 👋 Before you open this PR

Hi there, thanks SO MUCH for contributing!! 💛 This template helps us review your work quickly and give good feedback. It looks longer than it is, most PRs only need a few sections.

You own every line in this PR as if you typed it by hand. LLMs are allowed here, they're helpful tools, but the human opening the PR is the one we'll be talking to in review, so we just want to make sure that the person understands the code. The more an LLM did, the more we ask you to show that understanding. That's it. No gotchas.

How to contribute: https://github.com/MarkAStevens04/cloudflare-kinetics-editor/blob/main/CONTRIBUTING.md


## 🤔 Section A - Description
*(Everyone fills this out.)*

A clear and concise description of what this PR does.

Use this section for review hints, explanations or discussion points/todos.

- What changed
- Why
- Anything reviewers should know (review hints, open questions, TODOs, discussion points, etc.)

## ✅ Verification

*(Everyone fills this out. It's the fastest way for us to trust your change!)*

Show us it works! Paste a screenshot, test results, etc. Even just a list of steps you did to make sure your code is working! 

[ ] I ran this code locally and it does what the description says

## 🔎 Quick Self Check
*(Everyone does this, a quick 30 second pass before you submit)*

- [ ] This PR is **one logical change**. (Big or architectural? Let's chat in an issue first before writing code 🙏)
- [ ] No leftover dead code, debugging prints, or unused imports
- [ ] Every import / API / dependency I reference actually exists and is already available
- [ ] Comments explain *why* not what, and the style matches the surrounding file.
- [ ] I used existing functions and components where possible.
- [ ] My style matches the surrounding code to the best of my ability
- [ ] I could re-derive any non-obvious line if you asked me to

## 🤖 Used an LLM? 
*(Skip this if you wrote everything yourself!)*

Telling us where you used an LLM isn't a strike against you. It's helpful context, and we appreciate the honesty! 💬

- **Where an LLM helped:** (which files / sections, roughly)
- **The gist**: in your own words, what does that code do and why did you take this approach over the obvious alternative? 

You don't need to justify every line, just the parts that are complex, risky, or that someone might reasonably question. If a chunk of generated code is doing something non-obvious, walk us through your thinking there. 

## 🔁 When we request changes

We review to make the code better, not to nitpick. We'd also love to help you grow as a contributor! 🌱 When we leave comments:

- **Please reply inline and update *this* PR.** Push new commits to the same branch.
- **Please don't close this and open a brand-new PR** with regenerated code. We lose the whole conversation that way, and it usually reintroduces the things we just fixed. Iterating in place is faster for both of us.

Thanks again for contributing, we're glad you're here!! 🎉


## 📜 BioBuilder Contributor License Agreement

I give Mark Stevens and BioBuilder permission to license my contributions on any terms they like. I am giving them this license in order to make it possible for them to accept my contributions into their project.

**_As far as the law allows, my contributions come as is, without any warranty or condition, and I will not be liable to anyone for any damages related to this software or this license, under any kind of legal claim._**

[MarkAStevens04]

Looks good, just please fill out that PR template in the comment above and I'll be able to give a more accurate review!

[MarkAStevens04]

Thanks for this formatting cleanup!

[github-actions]

👋 Thank you SO MUCH for contributing!! We ask that you fill out the following template so that we can review your code easier and get it live as quickly as possible! 💛

Here's what still needs attention:

• The ## 📜 BioBuilder Contributor License Agreement section has been altered. It must be left exactly as it appears in the template.

📋 Click to expand the full template

Closes {LINK TO GH ISSUE}

## 👋 Before you open this PR

Hi there, thanks SO MUCH for contributing!! 💛 This template helps us review your work quickly and give good feedback. It looks longer than it is, most PRs only need a few sections.

You own every line in this PR as if you typed it by hand. LLMs are allowed here, they're helpful tools, but the human opening the PR is the one we'll be talking to in review, so we just want to make sure that the person understands the code. The more an LLM did, the more we ask you to show that understanding. That's it. No gotchas.

How to contribute: https://github.com/MarkAStevens04/cloudflare-kinetics-editor/blob/main/CONTRIBUTING.md


## 🤔 Section A - Description
*(Everyone fills this out.)*

A clear and concise description of what this PR does.

Use this section for review hints, explanations or discussion points/todos.

- What changed
- Why
- Anything reviewers should know (review hints, open questions, TODOs, discussion points, etc.)

## ✅ Verification

*(Everyone fills this out. It's the fastest way for us to trust your change!)*

Show us it works! Paste a screenshot, test results, etc. Even just a list of steps you did to make sure your code is working! 

[ ] I ran this code locally and it does what the description says

## 🔎 Quick Self Check
*(Everyone does this, a quick 30 second pass before you submit)*

- [ ] This PR is **one logical change**. (Big or architectural? Let's chat in an issue first before writing code 🙏)
- [ ] No leftover dead code, debugging prints, or unused imports
- [ ] Every import / API / dependency I reference actually exists and is already available
- [ ] Comments explain *why* not what, and the style matches the surrounding file.
- [ ] I used existing functions and components where possible.
- [ ] My style matches the surrounding code to the best of my ability
- [ ] I could re-derive any non-obvious line if you asked me to

## 🤖 Used an LLM? 
*(Skip this if you wrote everything yourself!)*

Telling us where you used an LLM isn't a strike against you. It's helpful context, and we appreciate the honesty! 💬

- **Where an LLM helped:** (which files / sections, roughly)
- **The gist**: in your own words, what does that code do and why did you take this approach over the obvious alternative? 

You don't need to justify every line, just the parts that are complex, risky, or that someone might reasonably question. If a chunk of generated code is doing something non-obvious, walk us through your thinking there. 

## 🔁 When we request changes

We review to make the code better, not to nitpick. We'd also love to help you grow as a contributor! 🌱 When we leave comments:

- **Please reply inline and update *this* PR.** Push new commits to the same branch.
- **Please don't close this and open a brand-new PR** with regenerated code. We lose the whole conversation that way, and it usually reintroduces the things we just fixed. Iterating in place is faster for both of us.

Thanks again for contributing, we're glad you're here!! 🎉


## 📜 BioBuilder Contributor License Agreement

I give Mark Stevens and BioBuilder permission to license my contributions on any terms they like. I am giving them this license in order to make it possible for them to accept my contributions into their project.

**_As far as the law allows, my contributions come as is, without any warranty or condition, and I will not be liable to anyone for any damages related to this software or this license, under any kind of legal claim._**

This check re-runs automatically when you edit the description, so it'll clear once everything's in place.

[MarkAStevens04]

Hey @nivedita9009! I'm really proud of the progress you've made and I'm sad to see this was closed. Feel free to open a new PR or reopen this one if you'd still like your changes merged! ❤️

I'm going to unassign the issue since you closed the PR, but let me know if you'd like me to re-assign it to you and I'd be more than happy 😊