fix: SQLite has no ADD COLUMN IF NOT EXISTS, crashed on startup

Conflated CREATE TABLE/INDEX's IF NOT EXISTS support with ALTER
TABLE ADD COLUMN, which SQLite has never supported -- syntax error,
not a version issue (confirmed on 3.49.2). Check pragma table_info
for the column first instead. Verified against both a fresh DB and
one simulating the existing pre-migration production schema, and
confirmed idempotent on a second open.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/api/src/db/index.ts

@@ -55,8 +55,14 @@ export function openDb(path: string): Database.Database {
     );
   `);
   // Migration for the devices table pre-dating mdns_hostname (CREATE TABLE IF
-  // NOT EXISTS above doesn't touch already-existing tables).
+  // NOT EXISTS above doesn't touch already-existing tables). SQLite's ALTER
-  db.exec(`ALTER TABLE devices ADD COLUMN IF NOT EXISTS mdns_hostname TEXT`);
+  // TABLE ADD COLUMN has no IF NOT EXISTS clause (unlike CREATE TABLE/INDEX),
+  // so check first -- confirmed the hard way, "ADD COLUMN IF NOT EXISTS" is a
+  // syntax error even on a SQLite version otherwise new enough for it.
+  const hasMdnsColumn = (db.pragma("table_info(devices)") as { name: string }[]).some(
+    (c) => c.name === "mdns_hostname"
+  );
+  if (!hasMdnsColumn) db.exec(`ALTER TABLE devices ADD COLUMN mdns_hostname TEXT`);
   return db;
 }