feat: CSV export and employee payslip view

Two audiences the super-user API did not serve.

Accounting gets `GET /api/v1/payouts.csv`, filterable by contract, status
and date range. The range bounds the *payday* rather than the row
timestamp, so a period contains the paydays that belong to it even when one
of them took three days of retries to settle — otherwise a late retry lands
in the wrong month's export.

Every exported field is neutralised against spreadsheet formula injection.
`detail` carries exception text and the memo carries operator input, and a
cell beginning `=`, `+`, `-` or `@` executes when the file is opened. Worth
the eight lines: this file is written specifically to be opened in somebody
else's spreadsheet.

Employees get `/api/v1/my/payouts`, `/my/payouts.csv` and `/my/contracts`
on a **separate router** gated by a wallet invoice key rather than by
super-user rights. Separate router so it cannot inherit — or accidentally
shed — the wrong gate. Scoped to the wallet rather than the account because
an invoice key names exactly one wallet, leaving no lookup that could widen
the result to a sibling wallet the key does not cover.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018jy52j9GRZ6XKa1Zt21LLj

crud.py

@@ -101,17 +101,37 @@ async def create_payout(payout: Payout) -> Payout:
 
 async def get_payouts(
     contract_id: str | None = None,
+    employee_wallet: str | None = None,
     status: PayoutStatus | None = None,
+    since: str | None = None,
+    until: str | None = None,
     limit: int = 200,
 ) -> list[Payout]:
+    """Ledger rows, newest first.
+
+    `since`/`until` bound the **payday**, not the row's creation time: an
+    accounting period is about which paydays fall in it, and a payday that
+    was retried for three days would otherwise land in the wrong month.
+    Both are inclusive `YYYY-MM-DD`, which compares correctly as a string
+    because that is the only format `payday` is ever written in.
+    """
     where = []
     values: dict = {}
     if contract_id:
         where.append("contract_id = :cid")
         values["cid"] = contract_id
+    if employee_wallet:
+        where.append("employee_wallet = :wid")
+        values["wid"] = employee_wallet
     if status:
         where.append("status = :status")
         values["status"] = status.value
+    if since:
+        where.append("payday >= :since")
+        values["since"] = since
+    if until:
+        where.append("payday <= :until")
+        values["until"] = until
     clause = f"WHERE {' AND '.join(where)}" if where else ""
     return await db.fetchall(
         f"SELECT * FROM payroll.payouts {clause} "