feat: add observability api foundation

crates/crank-registry/src/migrations.rs

@@ -385,5 +385,64 @@ pub async fn apply_postgres(pool: &PgPool) -> Result<(), sqlx::Error> {
     .execute(pool)
     .await?;
 
+    query(
+        "create table if not exists invocation_logs (
+            id text primary key,
+            workspace_id text not null references workspaces(id) on delete cascade,
+            agent_id text null references agents(id) on delete set null,
+            operation_id text not null references operations(id) on delete cascade,
+            source text not null,
+            level text not null,
+            status text not null,
+            tool_name text not null,
+            message text not null,
+            request_id text null,
+            status_code integer null,
+            duration_ms bigint not null,
+            error_kind text null,
+            request_preview_json jsonb not null,
+            response_preview_json jsonb not null,
+            created_at timestamptz not null
+        )",
+    )
+    .execute(pool)
+    .await?;
+
+    query(
+        "create index if not exists invocation_logs_workspace_created_idx on invocation_logs(workspace_id, created_at desc)",
+    )
+    .execute(pool)
+    .await?;
+
+    query(
+        "create index if not exists invocation_logs_workspace_operation_created_idx on invocation_logs(workspace_id, operation_id, created_at desc)",
+    )
+    .execute(pool)
+    .await?;
+
+    query(
+        "create index if not exists invocation_logs_workspace_agent_created_idx on invocation_logs(workspace_id, agent_id, created_at desc)",
+    )
+    .execute(pool)
+    .await?;
+
+    query(
+        "create table if not exists usage_rollups (
+            workspace_id text not null references workspaces(id) on delete cascade,
+            agent_id text null references agents(id) on delete cascade,
+            operation_id text null references operations(id) on delete cascade,
+            period text not null,
+            calls_total bigint not null,
+            calls_ok bigint not null,
+            calls_error bigint not null,
+            p50_ms bigint not null,
+            p95_ms bigint not null,
+            p99_ms bigint not null,
+            updated_at timestamptz not null
+        )",
+    )
+    .execute(pool)
+    .await?;
+
     Ok(())
 }