fix(corpus): committee decisions are persuasive, never binding (INV-DM7)

ועדת-ערר decisions (source_kind=internal_committee / source_type=
appeals_committee) are persuasive authority — they do not bind another
committee, nor the committee itself. The stored is_binding column wrongly
defaulted to True across the FastAPI form + service/db layers, so 46 of 92
committee rows were marked binding and got the BINDING halacha-extraction
prompt. Authority is structural for this source (INV-DM7) — normalize at the
source (G1), not trust the input.

Changes:
- db.create_internal_committee_decision: coerce is_binding=False (structural)
- db.create_external_case_law: coerce False when source_type=appeals_committee
- db.update_case_law: coerce False when a patch relabels source_type=
  appeals_committee (Gemini reclassification path)
- internal_decisions.migrate_from_external_corpus: set is_binding=FALSE on
  the external→internal reclassification UPDATE
- service + FastAPI-form defaults: True → False for the internal path
- SCHEMA_V42: backfill legacy committee rows (is_binding True→False) +
  CHECK constraint case_law_committee_not_binding_check so a binding
  committee row can never be written again ("so it doesn't recur")
- spec: X8-field-provenance aligned to INV-DM7

Verified against live DB in a rollback transaction: 46 rows flip to 0;
court_ruling (239) + cited_only (31) unaffected; binding-committee INSERT
rejected by the constraint.

Invariants: INV-DM7 (authority ⊥ rule-type) · G1 (normalize at source) ·
G2 (single source of truth, no parallel path).

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

web/app.py

@@ -7141,7 +7141,7 @@ async def internal_decisions_upload(
     practice_area: str = Form(""),
     appeal_subtype: str = Form(""),
     subject_tags: str = Form("[]"),
-    is_binding: bool = Form(True),
+    is_binding: bool = Form(False),  # INV-DM7: committee = persuasive (coerced at db too)
     summary: str = Form(""),
 ):
     """Upload a planning appeals-committee decision to the internal corpus.