Stop previewing received Taildrop images

[rcssdy]

Problem

The Taildrop receiver passes received image files directly to the notification service with --image.

This causes Quickshell to decode received image contents automatically, before the recipient interacts with the notification. Some Qt image decoders can allocate memory proportional to the encoded file size even when a small sourceSize is requested, allowing a sufficiently large received image to exhaust Quickshell’s available memory.

Fix

Use the existing generic file glyph for every received Taildrop file instead of attaching image files as notification previews.

The existing behavior is otherwise preserved:

• files are still saved to the downloads directory
• notifications remain persistent
• clicking a notification still opens the received file

Tests

• bash test/shell.d/tailscale-receive-test.sh
• bash -n bin/omarchy-tailscale-receive test/shell.d/tailscale-receive-test.sh
• git diff --check

The regression test now verifies that received images are not passed to the notification service through --image.