Add community node data layer: tables, usage ledger, bandwidth_sharing consent

Phase 2 of plan.md. Seven node_* tables with atomic device, bandwidth and XP caps,
a transactional job ledger whose lifetime totals survive pruning, clamped donor
settings, and the bandwidth_sharing consent kind. The acceptance service now has
an explicit exclusion list so it can never grant that consent.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

tests/unit/services/acceptance/agreements.py

@@ -3,6 +3,7 @@
 from devplacepy.database import CONSENT_KINDS
 from devplacepy.services.acceptance.agreements import (
     AGREEMENTS,
+    EXCLUDED_CONSENTS,
     agreement_for,
     label_for,
     setting_key,
@@ -11,7 +12,10 @@ from devplacepy.services.acceptance.service import AcceptanceService
 
 
 def test_every_consent_kind_is_classified_as_an_agreement():
-    assert {agreement.kind for agreement in AGREEMENTS} == set(CONSENT_KINDS)
+    classified = {agreement.kind for agreement in AGREEMENTS}
+    assert classified.isdisjoint(EXCLUDED_CONSENTS)
+    assert classified | set(EXCLUDED_CONSENTS) == set(CONSENT_KINDS)
+    assert all(EXCLUDED_CONSENTS.values())
 
 
 def test_setting_keys_are_unique_and_namespaced():