Add admin users, BYOC teams, hosts schema, and Redis for host registration

Introduce three migrations: admin permissions (is_admin + permissions table),
BYOC team tracking, and multi-host support (hosts, host_tokens, host_tags).
Add Redis to dev infra and wire up client in control plane for ephemeral
host registration tokens. Add go-redis dependency.

db/migrations/20260316203138_byoc_teams.sql

@@ -0,0 +1,9 @@
+-- +goose Up
+
+ALTER TABLE teams
+    ADD COLUMN is_byoc BOOLEAN NOT NULL DEFAULT FALSE;
+
+-- +goose Down
+
+ALTER TABLE teams
+    DROP COLUMN is_byoc;