feat: double audit — impersonated_by in audit_log

- db.js: add impersonated_by column to audit_log
- queries.js: logAudit accepts impersonatedBy, all CRUD pass it
- api/routes/entries.js: pass req.user.originalUserEmail as impersonatedBy
- При имперсонации: created_by=импактируемый, impersonated_by=админ

src/db.js

@@ -56,6 +56,7 @@ async function ensureSchema() {
       old_value    TEXT,
       new_value    TEXT,
       entry_id     INTEGER,
+      impersonated_by VARCHAR(255) DEFAULT NULL,
       created_at   TIMESTAMPTZ NOT NULL DEFAULT NOW()
     );
     CREATE INDEX IF NOT EXISTS idx_audit_company_time ON audit_log(company_id, created_at DESC);