ipx-directory: the directory of public podcasts ipx servers share (#204)

A new crate and service, crates/directory, live at ipx-dir.sdf1.net. ipx
servers send the public feeds their people subscribe to (POST /v1/snapshot,
replacing what that token sent before); the directory fetches each feed's
title, artwork, category, description and latest twenty items every six
hours with ipx-feed, and lists them A to Z and by subscribers summed over
every server. It holds metadata only, never a file or a file's address.

Tokens are in its config file as SHA-256 hashes, each ro, rw or rwa, and
the file is read again within a minute of a change, so adding and revoking
one is an edit and nothing else; a revoked token takes its server's counts.
At first they were to come from environment variables, which would have
meant recreating the container to add one. A file that does not load keeps
the tokens as they were.

Every address sent is checked with ipx_feed::url_looks_private, the check
ipx makes before sending, so one server's miss does not publish a paid feed
to every other; an rwa token can remove and block what both miss.

Deployed: ipx-directory in the ipx Arcane project, database ipx_directory
(its own login) on the databases project's Postgres, which db-backup
already covers, and a tunnel route with no Access in front. The store's
tests run on Postgres as well as SQLite when IPX_TEST_DATABASE_URL is set.

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

Dockerfile.directory

@@ -0,0 +1,23 @@
+# ipx-directory (#204). Built from the repo's root: docker buildx build -f Dockerfile.directory .
+# No node here: only ipx's own build runs web/build.mjs.
+FROM rust:1-slim-trixie AS build
+# SQLite is compiled from source for sqlx, which needs a C toolchain.
+RUN apt-get update && apt-get install -y --no-install-recommends build-essential \
+    && rm -rf /var/lib/apt/lists/*
+WORKDIR /src
+# Every member of the workspace, since cargo reads them all to build one.
+# ponytail: no dependency layer, so each build compiles sea-orm again; add the stub trick from
+# the main Dockerfile if builds get slow enough to matter.
+COPY Cargo.toml Cargo.lock ./
+COPY crates ./crates
+RUN cargo build --release --locked -p ipx-directory
+
+FROM debian:trixie-slim
+RUN apt-get update && apt-get install -y --no-install-recommends ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+COPY --from=build /src/target/release/ipx-directory /usr/local/bin/ipx-directory
+ENV DIRECTORY_CONFIG=/config/directory.toml
+# Unraid's nobody:users. It writes nothing to disk: the database is elsewhere.
+USER 99:100
+EXPOSE 8100
+CMD ["ipx-directory"]