feat: audit space activity

internal/db/migrations/00009_create_space_audit_logs_table.sql

@@ -0,0 +1,21 @@
+-- +goose Up
+-- +goose StatementBegin
+CREATE TABLE space_audit_logs (
+    id TEXT PRIMARY KEY NOT NULL,
+    space_id TEXT NOT NULL,
+    actor_id TEXT REFERENCES users(id) ON DELETE SET NULL,
+    action TEXT NOT NULL,
+    target_user_id TEXT REFERENCES users(id) ON DELETE SET NULL,
+    target_email TEXT,
+    metadata JSONB NOT NULL DEFAULT '{}'::jsonb,
+    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
+);
+
+CREATE INDEX idx_space_audit_logs_space_id_created_at
+    ON space_audit_logs (space_id, created_at DESC);
+-- +goose StatementEnd
+
+-- +goose Down
+-- +goose StatementBegin
+DROP TABLE space_audit_logs;
+-- +goose StatementEnd