feat(pairing): m010 schema — bunker pairing columns on dca_machines

Schema checkpoint for seed-URL pairing (S0 / #9; spire-side bitspire#52),
model A1 — the spire's signing key lives in the operator's nsecbunkerd,
not on the spire's disk.

dca_machines gains:
  - bunker_spire_key_name — the spire's key name in the bunker
    (spire-<machine_id>); used to re-issue connect tokens on re-pair.
  - paired_at — last successful pair; NULL = never paired.

Both nullable, idempotent column-probe add (m009 pattern). Machine model
gains the matching optional fields. Validated on the regtest dev db
(columns present, migrations clean); 191 tests green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

migrations.py

@@ -735,3 +735,44 @@ async def m009_split_fee_fractions_by_direction(db):
         await db.execute(
             "ALTER TABLE spirekeeper.super_config DROP COLUMN super_fee_fraction"
         )
+
+
+async def m010_add_machine_bunker_pairing(db):
+    """Add NIP-46 bunker-pairing columns to dca_machines for seed-URL
+    pairing (S0 / aiolabs/spirekeeper#9; spire-side aiolabs/bitspire#52).
+
+    Under the chosen model (A1, decided 2026-06-16), the spire's signing
+    key lives inside the operator's nsecbunkerd rather than on the spire's
+    disk. `pair_machine` mints a per-spire key in the bunker, issues a
+    scoped NIP-46 connect token, and hands the spire a one-shot seed URL
+    embedding a `bunker://` connection. The spire then self-signs all its
+    events (kind-21000 RPC, kind-30078 beacon/cassette-state) as its own
+    bunker-held key; lnbits' path-B roster routes that npub to the
+    operator's wallet.
+
+    ("spire" = a bitSpire machine; the legacy Lamassu term was "ATM".)
+
+      - bunker_spire_key_name — the spire's key name inside the bunker
+        (`spire-<machine_id>`). Used to re-issue a connect token on
+        re-pair and (once the admin client grows a revoke RPC) to revoke
+        spire access.
+      - paired_at — timestamp of the last successful pair. NULL = the
+        machine row exists but no bunker key has been minted yet.
+
+    Both nullable: machines created before this migration, and registered
+    -but-never-paired machines, carry NULL until first pair. Idempotent
+    column-probe pattern (same shape as m009).
+    """
+    additions = [
+        ("dca_machines", "bunker_spire_key_name", "TEXT"),
+        ("dca_machines", "paired_at", "TIMESTAMP"),
+    ]
+    for table, col, coltype in additions:
+        try:
+            await db.fetchone(f"SELECT {col} FROM spirekeeper.{table} LIMIT 1")
+            continue
+        except Exception:
+            pass
+        await db.execute(
+            f"ALTER TABLE spirekeeper.{table} ADD COLUMN {col} {coltype}"
+        )

models.py

@@ -56,6 +56,9 @@ class Machine(BaseModel):
     is_active: bool
     operator_cash_in_fee_fraction: float = 0.0
     operator_cash_out_fee_fraction: float = 0.0
+    # NIP-46 bunker pairing (S0 / #9). NULL until the spire is first paired.
+    bunker_spire_key_name: str | None = None
+    paired_at: datetime | None = None
     created_at: datetime
     updated_at: datetime