fix(trips): a trip figure must only count what the owner is owed

The per-trip owed number shipped in 689fadc counted every split on every
trip transaction regardless of who paid, so it silently mixed debts owed to
different people under one label.

On Europe 2026 that meant Molina "owed" $21,572.12, of which $1,605.49 was
her share of rows Sonu paid for — a real debt, but between the other two
participants, and one they had already settled directly (split_payments id
5, Molina -> Sonu, exactly $1,605.49). A participant's own share of a row
they themselves paid for was in there too, which is nobody's debt at all.

Both sides needed scoping, not just one: the owed side to rows this owner
paid for, and the paid side to payments made to this owner. Scoping only
the first would have let a Molina -> Sonu payment reduce what Molina owes
the owner.

The corrected figures reproduce a number derived independently, months of
data apart: Molina now reads -$816.16 on Europe, matching her known
overpayment to the cent ($19,966.63 of splits against $20,782.79 paid).
Sonu goes from $8,793.10 to $1,084.61, and the owner correctly disappears
from a list of people who owe the owner.

Found by checking a household total against what the app had been showing
all along — the query was gross, gave a number about twice the real one,
and I had quoted it as "owed". Worth stating plainly: the defect was not in
the number the app displayed, it was in the number I computed to explain it.

src/__tests__/integration/queries.test.ts

@@ -411,3 +411,58 @@ describe("getTripAnalytics — per-trip settlement", () => {
     expect(bob === undefined || Number(bob.owed) === 0).toBe(true);
   });
 });
+
+describe("getTripAnalytics — owner scoping", () => {
+  it("ignores a trip expense someone else paid for", async () => {
+    const { ownerId, otherId } = await seedParticipants(pool);
+    const trip = await pool.query(
+      `INSERT INTO trips (owner_id, name) VALUES ($1, 'Owner Scope Trip') RETURNING id`,
+      [ownerId]
+    );
+    const tripId = trip.rows[0].id as number;
+
+    // Bob paid this one. Alice's share of it is a debt Alice owes Bob — it is
+    // not something Bob owes Alice, so it must not appear on Alice's trip view.
+    const bobPaid = await insertTransaction(pool, otherId, { amount: 500, category: "travel" });
+    await pool.query(`INSERT INTO transaction_overrides (transaction_id, trip_id) VALUES ($1, $2)`, [bobPaid, tripId]);
+    await pool.query(
+      `INSERT INTO transaction_splits (transaction_id, participant_id, share_percent)
+       VALUES ($1, $2, 50), ($1, $3, 50)`,
+      [bobPaid, ownerId, otherId]
+    );
+
+    const { participant_splits } = await getTripAnalytics(tripId, ownerId);
+    const bob = participant_splits.find((r) => r.participant_id === otherId);
+    expect(bob === undefined || Number(bob.owed) === 0).toBe(true);
+  });
+
+  it("ignores a payment settled between the other two participants", async () => {
+    const { ownerId, otherId } = await seedParticipants(pool);
+    const third = await pool.query(
+      `INSERT INTO participants (name, email) VALUES ('Carol', 'carol@example.com') RETURNING id`
+    );
+    const carolId = third.rows[0].id as number;
+    const trip = await pool.query(
+      `INSERT INTO trips (owner_id, name) VALUES ($1, 'Third Party Trip') RETURNING id`,
+      [ownerId]
+    );
+    const tripId = trip.rows[0].id as number;
+
+    const txId = await insertTransaction(pool, ownerId, { amount: 300, category: "travel" });
+    await pool.query(`INSERT INTO transaction_overrides (transaction_id, trip_id) VALUES ($1, $2)`, [txId, tripId]);
+    await pool.query(
+      `INSERT INTO transaction_splits (transaction_id, participant_id, share_percent) VALUES ($1, $2, 50)`,
+      [txId, carolId]
+    );
+    // Carol pays Bob, not the owner. Carol still owes the owner $150.
+    await pool.query(
+      `INSERT INTO split_payments (from_participant_id, to_participant_id, amount, payment_date, trip_id)
+       VALUES ($1, $2, 150, '2026-03-15', $3)`,
+      [carolId, otherId, tripId]
+    );
+
+    const { participant_splits } = await getTripAnalytics(tripId, ownerId);
+    const carol = participant_splits.find((r) => r.participant_id === carolId);
+    expect(Number(carol!.owed)).toBeCloseTo(150);
+  });
+});