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/20260316203142_hosts.sql

@@ -0,0 +1,47 @@
+-- +goose Up
+
+CREATE TABLE hosts (
+    id                TEXT PRIMARY KEY,
+    type              TEXT NOT NULL DEFAULT 'regular',  -- 'regular' or 'byoc'
+    team_id           TEXT REFERENCES teams(id) ON DELETE SET NULL,
+    provider          TEXT,
+    availability_zone TEXT,
+    arch              TEXT,
+    cpu_cores         INTEGER,
+    memory_mb         INTEGER,
+    disk_gb           INTEGER,
+    address           TEXT,                             -- ip:port of host agent
+    status            TEXT NOT NULL DEFAULT 'pending',  -- 'pending', 'online', 'offline', 'draining'
+    last_heartbeat_at TIMESTAMPTZ,
+    metadata          JSONB NOT NULL DEFAULT '{}',
+    created_by        TEXT NOT NULL REFERENCES users(id),
+    created_at        TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at        TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE host_tokens (
+    id         TEXT PRIMARY KEY,
+    host_id    TEXT NOT NULL REFERENCES hosts(id) ON DELETE CASCADE,
+    created_by TEXT NOT NULL REFERENCES users(id),
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    expires_at TIMESTAMPTZ NOT NULL,
+    used_at    TIMESTAMPTZ
+);
+
+CREATE TABLE host_tags (
+    host_id TEXT NOT NULL REFERENCES hosts(id) ON DELETE CASCADE,
+    tag     TEXT NOT NULL,
+    PRIMARY KEY (host_id, tag)
+);
+
+CREATE INDEX idx_hosts_type ON hosts(type);
+CREATE INDEX idx_hosts_team ON hosts(team_id);
+CREATE INDEX idx_hosts_status ON hosts(status);
+CREATE INDEX idx_host_tokens_host ON host_tokens(host_id);
+CREATE INDEX idx_host_tags_tag ON host_tags(tag);
+
+-- +goose Down
+
+DROP TABLE host_tags;
+DROP TABLE host_tokens;
+DROP TABLE hosts;