[Feature]: Manually add a listing (e.g. by URL) #492

Related Problem

I'd like to be able to add a listing to Fredy by hand, e.g. one I found myself on a portal, got from a friend, or that my jobs didn't pick up.
Right now listings only get into Fredy through jobs. If I want to track a specific listing, I have to build a very narrow search job that happens to include it, run it, and then disable it again.

Proposed Feature

An "Add listing" option in the listings view where I paste the listing URL.

And than:

1. Fredy recognizes the provider from the URL (ImmoScout, Immowelt, Kleinanzeigen, …).
2. It fetches the details the same way a job would (title, price, size, address, images).
3. The listing then shows up like any other, with watchlist, notes, attachments, price history, active check and so on.

Alternatives Considered

No response

Benefits

• Helps with missed listings: If a job misses a listing (filter too narrow, provider changed its layout, listing was only online briefly), it can still be added and followed.
• Uses existing features: Notes, watchlist, attachments, price history, the active/inactive check and the finance calculation then also work for listings that no job found.
• Everything in one place: Listings found outside Fredy (shared by friends, seen on social media, from a portal Fredy doesn't cover) can be tracked next to all the others instead of in bookmarks or spreadsheets.

Additional Context

No response