fix: don't error on unknown files

[bouassaba]

Sorry guys, I ended up creating a Swiss knife here 🇨🇭🙈

• Don't show an error when a file is unknown.
• No longer consider failed-to-create-thumbnail an error, so the user can open the file anyways if there is a preview for it (one case is if the CLI we use to create thunbnails for 3D models using WebKit fails).
• Button + API endpoint to clean up (dismiss) all failed tasks.
• DISABLE_INSTALLER is now ENABLE_INSTALLER, so people running locally won't suddenly get stuff installing.
• Fix TIFF image preview.
• Fix CSV file preview;

Closes #174
Closes #168
Closes #166
Closes #167

Here it gives no error, the file can be downloaded but cannot be previewed:

Before one had to clean these up one by one: