feat(ui): add identity management for tenants and users

* Implement tenant and user creation in IdentityPage
* Add API calls for managing tenants and users
* Introduce tenant-scoped API requests
* Update sidebar to include identity navigation
* Create BooleanStatusBadge component for key status

migrations/120_identity_tenancy.sql

@@ -0,0 +1,31 @@
+create table if not exists tenants (
+    id text primary key,
+    name text not null unique,
+    created_at timestamptz not null default now()
+);
+
+create table if not exists tenant_users (
+    id text primary key,
+    tenant_id text not null references tenants(id),
+    name text not null,
+    email text,
+    created_at timestamptz not null default now(),
+    unique (tenant_id, email)
+);
+
+create index if not exists tenant_users_tenant_id_idx on tenant_users (tenant_id);
+
+create table if not exists api_key_assignments (
+    key_id text primary key,
+    tenant_id text not null references tenants(id),
+    user_id text references tenant_users(id),
+    description text not null default '',
+    source text not null check (source in ('configured', 'managed')),
+    enabled boolean not null default true,
+    created_at timestamptz not null default now()
+);
+
+create table if not exists managed_api_keys (
+    key_id text primary key references api_key_assignments(key_id) on delete cascade,
+    secret_hash text not null
+);