Festpreis-Input-Fix, Archiv-Teilen (read-only)

backend/src/db.js

@@ -246,4 +246,18 @@ if (msgCols2.length && !msgCols2.includes('read_by_recipient')) {
   db.exec("ALTER TABLE messages ADD COLUMN read_by_recipient INTEGER NOT NULL DEFAULT 0");
 }
 
+// ── Kalkulator-Shares ─────────────────────────────────────────────────────────
+if (!db.prepare("SELECT name FROM sqlite_master WHERE type='table' AND name='calculation_shares'").get()) {
+  db.exec(`
+    CREATE TABLE calculation_shares (
+      id          INTEGER PRIMARY KEY AUTOINCREMENT,
+      calc_id     INTEGER NOT NULL REFERENCES calculations(id) ON DELETE CASCADE,
+      shared_by   INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+      shared_with INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+      created_at  DATETIME DEFAULT NULL,
+      UNIQUE(calc_id, shared_with)
+    )
+  `);
+}
+
 module.exports = db;