[monitor-cli] feat: inspect persisted experiment ranges

[tardis-key]

What does this PR do?

• Adds a new CLI command: rl-insight data inspect
• Inspects persisted Prometheus and Tempo data offline
• Lists each project / experiment pair with its first and last timestamps

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    • monitor-api, monitor-cli, monitor-collector, monitor-server, monitor-config for online monitor changes
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Test

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API and Usage Example

# Inspect the default data directory
rl-insight data inspect

# Inspect a custom data directory
rl-insight data inspect --log-dir /path/to/rl-insight/data

Design & Code Changes

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