Adds crate-native follows, connections views, and the adoption-backed feed, with follow reconciliation, idempotent writes, and OAuth scope handling for pre-existing sessions.

Seeds twenty devnet collectors so the following/followers, feed, and record-detail UI render against real data. Note that alice.test gains a short demo password via ALICE_TEST_ACCOUNT_PASSWORD, default "alice", which is worth a look before merge.

Fifth of six PRs split out of demo/roadmap-wave. Targets stack/4-devnet-images.