v3: add backlinks between dumps (via either dump url or dump target url mentioned through dump description and dump comments)

api/db/migrations/0003_dump_backlinks.ts

@@ -0,0 +1,26 @@
+import type { DatabaseSync } from "node:sqlite";
+
+// Idempotent: safe to run against a fresh db (already created from schema.sql
+// with these) or an existing one that predates them.
+export function up(db: DatabaseSync): void {
+  db.exec(`CREATE TABLE IF NOT EXISTS dump_backlinks (
+    source_type  TEXT NOT NULL,
+    source_id    TEXT NOT NULL,
+    from_dump_id TEXT NOT NULL,
+    to_dump_id   TEXT NOT NULL,
+    created_at   TEXT NOT NULL,
+    PRIMARY KEY (source_type, source_id, to_dump_id),
+    FOREIGN KEY (from_dump_id) REFERENCES dumps(id) ON DELETE CASCADE,
+    FOREIGN KEY (to_dump_id)   REFERENCES dumps(id) ON DELETE CASCADE
+  );`);
+
+  db.exec(
+    `CREATE INDEX IF NOT EXISTS idx_dump_backlinks_to ON dump_backlinks(to_dump_id);`,
+  );
+  db.exec(
+    `CREATE INDEX IF NOT EXISTS idx_dump_backlinks_from ON dump_backlinks(from_dump_id);`,
+  );
+  db.exec(
+    `CREATE INDEX IF NOT EXISTS idx_dumps_url ON dumps(url);`,
+  );
+}