### System details

AMD Ryzen AI MAX+ 395 w/ Radeon 8060S, Omarchy 4.0.3-1

### What's wrong?

`omarchy-tailscale-receive` ignores the downloads directory configured in `~/.config/user-dirs.dirs` and recreates `~/Downloads` at every login.

**Steps to reproduce**

1. Set `XDG_DOWNLOAD_DIR="$HOME/dl"` in `~/.config/user-dirs.dirs` (`xdg-user-dir DOWNLOAD` prints `/home/user/dl`).
2. Delete `~/Downloads`.
3. Log out and back in, so `omarchy-tailscale-receive.service` starts with the graphical session.

**Expected:** the Taildrop staging directory is created at `~/dl/.omarchy-taildrop` and received files land in `~/dl`.

**Actual:** `~/Downloads/.omarchy-taildrop` is created and `~/Downloads` comes back every login.

**Cause**

`bin/omarchy-tailscale-receive` picks its directory from an environment variable only:

```bash
dir="${1:-${XDG_DOWNLOAD_DIR:-$HOME/Downloads}}"
```

`XDG_DOWNLOAD_DIR` is not a variable the session exports; it only exists as a line in `user-dirs.dirs`. The systemd user manager's environment (`systemctl --user show-environment`) does not contain it, so the service always takes the `$HOME/Downloads` fallback. The migration that enables the service (`migrations/1785101000.sh`) also hardcodes "Save incoming Taildrop files to ~/Downloads".

**Suggested fix**

Resolve the directory the same way the rest of the desktop does, e.g.

```bash
dir="${1:-$(xdg-user-dir DOWNLOAD)}"
```

with `$HOME/Downloads` only as a last resort if `xdg-user-dir` is unavailable. This is the same class of problem as #7733 / #8091 (provisioning recreating default XDG folders despite a customized `user-dirs.dirs`).

**Workaround**

A drop-in passes the directory explicitly and survives updates:

```ini
# ~/.config/systemd/user/omarchy-tailscale-receive.service.d/override.conf
[Service]
ExecStart=
ExecStart=/usr/bin/omarchy-tailscale-receive %h/dl
```