feat(cassettes): swap the count-publish endpoint for operation endpoints

The operator can no longer write a count. POST .../cassettes/ops records
one operation — refill, empty, recount, set_denomination — and publishes
the machine's recent window; GET .../cassettes/ops lists them newest
first with acked_at, so the dashboard can tell a delivered operation from
one merely sent.

POST .../cassettes/publish is gone, along with update_cassette_config and
UpsertCassetteConfigData. Nothing in the operator can now set a count,
which is the point: a value with one writer cannot be clobbered. Under
the old endpoint a dashboard form loaded before a dispense silently
discarded that dispense on publish, and neither side could detect it —
addressable events order by created_at at second granularity and a relay
returns OK for an event it then drops, so the losing writer is never told.

The op is recorded before the publish and is deliberately not rolled back
when the publish fails. It records something that physically happened;
notes went into a bay whether or not a relay was reachable. The window
carries recent operations rather than just the newest, so an op that
missed its own publish rides out with the next one.

Validation rejects an unpaired machine and a position the machine has not
reported. Bay count stays hardware-determined.

models.py

@@ -675,31 +675,6 @@ class CassetteConfig(BaseModel):
     state_event_id: str | None
 
 
-class UpsertCassetteConfigData(BaseModel):
-    """Operator edits a single cassette row's denomination or count from
-    the dashboard. Both fields optional; pass only those changed.
-    Position is not edited — it's the row's identity (hardware bay)."""
-
-    denomination: int | None = None
-    count: int | None = None
-
-    @validator("denomination")
-    def denomination_positive(cls, v):
-        if v is None:
-            return v
-        if v <= 0:
-            raise ValueError("denomination must be > 0")
-        return v
-
-    @validator("count")
-    def count_non_negative(cls, v):
-        if v is None:
-            return v
-        if v < 0:
-            raise ValueError("count must be >= 0")
-        return v
-
-
 class CassettePayloadRow(BaseModel):
     """One position's payload values in the wire-format
     `{"positions": {"<pos>": {"denomination", "count"}}}`."""