Cargo workspace: crates/ipx and a shared crates/feed (#202)

The first step of the split (#207). The daemon moves to crates/ipx unchanged;
feed.rs becomes crates/feed (ipx-feed), which the directory service (#204)
will share for its metadata refresher and its privacy check.

To stand alone, fetch takes the feed's address and its credentials instead
of ipx's config::Feed (config::Feed::auth gives them), collect_outlines
moves in with the OPML parsing, and the address half of looks_private is
feed::url_looks_private. ipx imports the crate as `feed` at its root, so
every crate::feed path is unchanged. The version is the workspace's, in the
root Cargo.toml.

Checked: cargo test on Postgres (118 + 29), tsc, page smoke, native bridge,
contrast and Playwright (72) pass; the image built from the new Dockerfile
is deployed and healthy.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Cargo.toml

@@ -1,9 +1,14 @@
-[package]
-name = "ipx"
+[workspace]
+members = ["crates/ipx", "crates/feed"]
+resolver = "3"
+
+# One version for the whole workspace: what a release sets, and what the logo's tooltip shows.
+[workspace.package]
 version = "0.12.1-dev"
 edition = "2024"
 
-[dependencies]
+[workspace.dependencies]
+ipx-feed = { path = "crates/feed" }
 ammonia = "4.1.4"
 anyhow = "1.0.104"
 argon2 = "0.6.0"