refactor(v2): canonical sat-amount vocabulary + delete Lamassu-era reverse-derivation

Cross-codebase decision logged at memory `reference_sat_amount_vocabulary.md`
and at `~/dev/coordination/log.md` (2026-05-26). Canonical names with
explicit units across satmachineadmin, lamassu-next, atm-tui:

  - `wire_sats` — actual Lightning payment amount (direction-agnostic;
                  was `gross_sats`, only "gross" for cash-out)
  - `principal_sats` — market-rate sats before commission (unchanged)
  - `fee_sats` — commission (was `commission_sats` internally;
                 already the wire format)
  - `fee_fraction` — commission rate as unit fraction in [0, 1]
                     (was `*_pct` / `fee_percent`; eliminates the
                     latent 100x bug from `feePercent * 100` on the
                     lamassu-next side)

Invariants enforced in bitspire._assert_sat_invariants on every
parsed settlement — range (all sats >= 0, 0 <= fee_fraction <= 1) +
direction-specific sum:

  - cash-out: wire_sats == principal_sats + fee_sats
  - cash-in:  wire_sats == principal_sats - fee_sats
              AND fee_sats <= principal_sats

Breaches raise SettlementInvariantError; tasks._handle_payment
records the row as `status='rejected'` with the exception message
and skips distribution. Attribution failure path symmetric.

Schema changes (m001 + m006):

  - dca_settlements.gross_sats              -> wire_sats
  - dca_settlements.commission_sats         -> fee_sats
  - super_config.super_fee_pct              -> super_fee_fraction
  - dca_commission_splits.pct               -> fraction
  - dca_machines.fallback_commission_pct    DROPPED (obsolete)
  - dca_settlements.used_fallback_split     DROPPED (obsolete)

m006 idempotently renames + drops columns on existing installs;
m001 lays down the canonical schema for fresh installs.

Obsolete code removed (Lamassu-era reverse-derivation):

  - calculations.calculate_commission — back-derived principal+fee
    from gross-with-commission-baked-in. v2 stamps both directly.
  - calculations.calculate_exchange_rate — bitSpire stamps directly.
  - bitspire._parse_fallback — sole caller of calculate_commission.
  - Machine.fallback_commission_fraction — only read by _parse_fallback.
  - DcaSettlement.used_fallback_split — only written by _parse_fallback.

parse_settlement now raises SettlementMetadataError if Payment.extra
lacks the bitSpire stamp or required absolute sat fields. No silent
back-derivation; upstream-bug surfacing via dashboard rejection.

Frontend (JS + Quasar templates) updated for the column renames and
the removed fallback fields. Settlements table renders "Wire" + "Fee"
columns; the "(fallback split)" warning badge is gone.

Tests:
  - test_calculations.py: kept distribution tests; deleted
    calculate_commission + calculate_exchange_rate tests.
  - test_two_stage_split.py: renamed variables; rewrote docstring
    value literals (e.g. `super_fee_fraction=0.30` not `=30%`).
  - test_nostr_attribution.py: dropped fallback_commission_fraction
    from machine fixture.
  - 72/72 pass on regtest container.

Cross-codebase follow-ups tracked in coordination log:
  - lamassu-next: rename `fee_percent` -> `fee_fraction` on
    Payment.extra + state.db; drop the `* 100` at lightning.ts:780.
  - atm-tui: read `fee_fraction` column in db.zig.

Memory artefacts:
  - reference_sat_amount_vocabulary.md (canonical + invariants)
  - feedback_pct_to_fraction_renames_need_value_sweep.md (gotcha)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_nostr_attribution.py

@@ -37,7 +37,6 @@ def _machine(npub: str) -> Machine:
         location=None,
         fiat_code="EUR",
         is_active=True,
-        fallback_commission_pct=0.05,
         created_at=now,
         updated_at=now,
     )