[FEATURE][PLUGIN]: Add CLI for authoring and packaging plugins

[araujof]

🧭 Type of Feature

Please select the most appropriate category:

• Enhancement to existing functionality
• New feature or capability
• New MCP-compliant server
• New component or integration
• Developer tooling or test improvement
• Packaging, automation and deployment (ex: pypi, docker, quay.io, kubernetes, terraform)
• Other (please describe below)

🧭 Epic

Title: A CLI for authoring and packaging plugins
Goal: Enable developers to bootstrap, install, and package plugins via a simple CLI
Why now: This is part of a core set of capabilities for enabling developers to create their own plugins

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🙋♂️ User Story 1

As a: developer
I want: to author an external plugin
So that: I can extend the gateway to filter/transform requests based on pre-defined hooks

✅ Acceptance Criteria

Scenario: bootstrap a new plugin project
  Given an empty project directory `myplugin`
  When the interactive `mcpplugin bootstrap <options> myplugin` completes
  Then a plugin project repository should be created from template under `myplugin`

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🙋♂️ User Story 2

As a: developer
I want: to package an external plugin
So that: I can deploy it as an API server for standardized consumption by the gateway

✅ Acceptance Criteria

Scenario: package a plugin as a container image
  Given a plugin repo
  When `mcpplugin package <options>` completes
  A new API server container image is created for the plugin

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🔗 MCP Standards Check

• Change adheres to current MCP specifications
• No breaking changes to existing MCP-compliant integrations
• If deviations exist, please describe them below:

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📓 Additional Context

Plugins roadmap: #673