Process statistics omit “Followers” when only the process itself is followed #17564

Describe the bug

On a participatory process landing page, the Statistics content block does not show the Followers metric when users only follow the process itself (via the process “Follow” button), and there are no follows on followable resources inside components (proposals, meetings, debates, budget projects).

Because statistics with value 0 are filtered out, the Followers field is omitted entirely instead of showing the process-level follower count.

This contradicts:

1. The followers tooltip copy (“users who follow any part of this space”)
2. The query class comment for ParticipatoryProcessesStatsFollowersCount (“counts all Followers of a participatory process”)
3. Process creation behavior that adds organization admins as followers of the process

To Reproduce

1. Create a participatory process (or use one with no followable component follows).

2. Ensure the Statistics content block is enabled on the process landing page.

3. Follow the process itself with one or more users (or rely on admins auto-added as followers on create).

4. Do not follow any proposals/meetings/debates/projects inside the process (or have no such published components).

5. Open the public process landing page and check the Statistics section.
   Observe: Followers is missing (count resolves to 0 and is rejected).

6. On another process, follow at least one proposal (or other tagged followable resource).

7. Reload that process landing page.

Observe: Followers appears.

Expected behavior

Followers should include process-level follows (users following the participatory process), not only follows on component resources.

At minimum, a process that has process followers should show a non-zero Followers statistic and render the field.

Screenshots

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Stacktrace

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Extra data

Device: Desktop
Device OS: macOS
Browser: Chrome / Safari
Decidim Version: 0.31.6

Additional context

No response