## Summary
- Adds Bun JavaScript runtime (v1.2.15) to the dogfood image
- Installs Bun to /usr/local/bin to ensure persistence when /home/coder
is mounted
- Verified that Bun works correctly in the built container

## Test plan
1. Build the dogfood image with `cd dogfood/coder && docker build -t
codercom/oss-dogfood:test .`
2. Run the container with `docker run --rm -it codercom/oss-dogfood:test
bash`
3. Test Bun in the container with:
   - `bun --version` (should output 1.2.15)
- `cd /tmp && echo "console.log('Hello from Bun\!');" > test.js && bun
run test.js`

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <noreply@anthropic.com>

## Summary
- Fixes image build failure by adding fallback to kernel.org mirrors
when Ubuntu/Debian repositories fail
- Ensures unzip is available during Bun installation process
- Improves apt repository configuration to prevent 403 errors in CI

## Root Cause
The build was failing for two reasons:
1. Network issues with Ubuntu/Debian package repositories returning 403
Forbidden errors
2. Unzip package not being reliably available in the image layer where
Bun installation happens

## Fix
- Added fallback mirrors for apt repositories using kernel.org mirrors
- Explicitly installed unzip before using it in the Bun installation
- Added proper cleanup after package installations to keep image size
down

## Test plan
- The CI workflow that was previously failing should now succeed
- Build the dogfood image locally with `cd dogfood/coder && docker build
-t codercom/oss-dogfood:test .`
- Verify Bun is correctly installed and can be used

Fixes build failure from PR #18154 (original PR that added Bun)

🤖 Generated with [Claude Code](https://claude.ai/code)

---------

Co-authored-by: Claude <noreply@anthropic.com>