analytics: your share of what someone else paid is your spend

Every spend analytic gated on `OWNER_SCOPE = $1` and scaled by `mySplitOf`
*within* that gate, so ownership was a precondition for an expense being
yours. Half a grocery shop Sonu paid for counted as zero — in monthly,
daily, merchants, subscriptions, fees and the budget page. 167 rows /
$3,210.91 across Jan-Jul 2026, worst in April (+$1,354.83, the Europe
trips), while getParticipantBalances booked the matching debt correctly.
The app could say you owed her for a shop while insisting you had not
spent anything on it.

New MY_SPEND_SCOPE(): owner = me OR I hold a split. OWNER_SCOPE stays on
the things that measure an *account* rather than a person — the income
and investment lines, and the statement-level fee rollup.

myShare had to change with it, and widening the gate alone would have
been worse than the bug: its `100 - everyone else` fallback is the
payer's remainder, so on someone else's unsplit row it returns 100 and
moves their whole bill onto you. It now branches on ownership — my row
resolves as before; their row takes an explicit split row only, absent
meaning 0. That 0 is what makes the wider gate safe.

my_share_percent is deliberately not read on someone else's row: one
unscoped column, writable by anyone who can see the row, so "my" can
only mean the owner's. All 402 rows carrying one today are owner-side.

MY_SHARE_PCT mirrors myShare for the transactions list, which has no
viewer-scoped ts join; a test asserts the two agree across seven fixture
shapes.

No historical restatement — every non-owner split is 2026-dated, and the
1,266 pre-2026 SplitMyExpenses splits are all on rows you own.

Also fixes a latent failure in the NATIVE_CURRENCY test, which inserted a
statement relying on participant id 1 existing (owner_id is NOT NULL
DEFAULT 1 with an FK) and only passed when a sibling file had left one
behind. It now owns its fixture.

15 new integration tests; 189 integration + 130 unit green.

src/app/api/analytics/monthly/route.ts

@@ -3,6 +3,7 @@ import { getCurrentUser } from "@/lib/auth";
 import { queryRaw } from "@/lib/db";
 import {
   OWNER_SCOPE,
+  MY_SPEND_SCOPE,
   STATEMENTS_JOIN,
   EFFECTIVE_CATEGORY,
   EXCLUDE_NON_SPEND,
@@ -46,7 +47,7 @@ export async function GET(req: NextRequest) {
     LEFT JOIN transaction_overrides o ON o.transaction_id = t.id
     LEFT JOIN transaction_splits ts ON ts.transaction_id = t.id AND ts.participant_id = $1
     ${STATEMENTS_JOIN}
-    WHERE ${OWNER_SCOPE} = $1
+    WHERE ${MY_SPEND_SCOPE()}
       AND ${NET_SPEND_ROWS}
       AND ${EXCLUDE_NON_SPEND}
       AND ${EXCLUDE_RECONCILED_SOURCE}