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>

crates/feed/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "ipx-feed"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+anyhow.workspace = true
+atom_syndication.workspace = true
+chrono.workspace = true
+opml.workspace = true
+quick-xml.workspace = true
+reqwest.workspace = true
+rss.workspace = true
+serde_json.workspace = true
+tracing.workspace = true
+url.workspace = true
+
+[dev-dependencies]
+tokio.workspace = true