feat: embed error.html template and move loading to main

[emsearcy]

• Bundle error.html template using go:embed for self-contained binaries
• Move template loading from init() to main() after logging setup
• Remove template file copy from Dockerfile since templates are embedded
• Add proper error template initialization with structured logging
• Support ko builds with no external file dependencies
• Remove template copy from Dockerfile

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[Copilot]

Pull Request Overview

This PR embeds the error.html template directly into the binary using go:embed, eliminating the need for external template files at runtime. This change enables self-contained builds (like ko) and simplifies deployment.

Key changes:

• Template content is now embedded at compile time using go:embed directive
• Template initialization moved from init() to main() to ensure proper logging context
• Dockerfile no longer needs to copy template files since they're embedded in the binary

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
responses.go	Adds go:embed directive to bundle error.html template and refactors template initialization into a callable function
main.go	Calls initErrorTemplate() after logging setup to ensure template errors are properly logged
Dockerfile	Removes template file copy step since templates are now embedded in the binary

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