bug: stale instance entries accumulate in config when container is recreated

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### Describe the bug

## Description

When a container is removed externally (e.g. `docker stop && docker rm`) and
`microcks start` recreates it, the old instance entry is never removed from config.
A new entry is appended instead, causing duplicate instance records to accumulate.

### Expected behavior

_No response_

### Actual behavior

_No response_

### How to Reproduce?

## Steps to Reproduce

1. `./microcks start`
2. `docker stop microcks && docker rm microcks`
3. `./microcks start`
4. `cat ~/.config/microcks/config` two instance entries with same name but different container IDs

## Screenshots

## Root Cause

`RemoveInstance` matched by `Name` instead of `ContainerID`. Since the recreated
container has a new ID, `UpsertInstance` never finds a match and always appends.

### Microcks version or git rev

_No response_

### Install method (`docker-compose`, `helm chart`, `operator`, `docker-desktop extension`,...)

_No response_

### Additional information

_No response_

Start at the microcks start flow and trace RemoveInstance and UpsertInstance, using the configuration at ~/.config/microcks/config and the container recreation steps as the reproduction. Confirm that recreating a container with a new ID does not leave duplicate entries for the same instance name, then verify the config contains one current record after restarting.

Written by the indexing model from the issue text.