RFC: Workload upgrade detection and application (#68)

* Add RFC for workload upgrade detection and application

Propose server-side upgrade detection for MCP server workloads,
moving tag drift and env var drift logic from Studio's frontend
into the ToolHive backend. Adds thv upgrade CLI commands and
REST API endpoints so all clients benefit.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Juan Antonio Osorio <ozz@stacklok.com>

* Rename RFC to match PR number (THV-0068)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Juan Antonio Osorio <ozz@stacklok.com>

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Signed-off-by: Juan Antonio Osorio <ozz@stacklok.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: JAORMX