feat: add custom port

[daltonbr]

Now we can set this to run on other ports, other than the default one.
Closes #3

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.77%. Comparing base (a524509) to head (b68ceff).

Files with missing lines	Patch %	Lines
main.go	0.00%	10 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##             main       #5      +/-   ##
==========================================
- Coverage   76.72%   71.77%   -4.95%     
==========================================
  Files           3        3              
  Lines         116      124       +8     
==========================================
  Hits           89       89              
- Misses         20       28       +8     
  Partials        7        7              

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[Copilot]

Pull request overview

This PR adds support for configuring a custom HTTP server port via the PORT environment variable, allowing the server to run on ports other than the default 5000.

• Introduces PORT environment variable configuration in main.go
• Updates documentation with examples of using custom ports
• Provides Docker and local development examples for port configuration

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
main.go	Adds PORT environment variable reading with default fallback to 5000, updates server startup messages to use configured port
docs/DEVELOPMENT.md	Documents PORT environment variable usage with examples for local development and Docker deployment
README.md	Adds environment variables section documenting PORT configuration option

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