feat(go-services): inventory-go Phase C — ingestion (validated, isolated DB)

Wires the validated item-processor into the ingestion endpoints, writing to an
isolated inventory-go-db (never production):
- schema.go: faithful 7-table replica of inventory-service/database.py.
- ingest.go: /process-inventory (full replace), POST/DELETE single item, with the
  exact delete-then-insert flow, dynamic INSERT builder (quotes reserved "unique"),
  spell union (is_active), and item_raw_data verbatim. enhancements always inserts.
- compose: isolated inventory-go-db (postgres:14, 127.0.0.1:5435) + read-write
  inventory-go-shadow (:8773) that owns it; schema init on boot.

Validated by ingesting a recently-ingested character's items (from production's
original_json) into the shadow DB and diffing vs production: byte-identical —
items 243, combat 243, enhancements 243, ratings 6, requirements 19, spells 52
all match; 0 per-column mismatches across 243 items.

Finding: older production normalized rows can be STALE (predate the code reading
Decal keys 218103832/218103835); Go matches the CURRENT Python code, so validate
ingestion against recently-ingested characters.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

go-services/inventory-go/process.go

@@ -266,7 +266,7 @@ func (s *Server) processItem(raw map[string]any) map[string]any {
 		"items":        items,
 		"combat":       nullify(combat, sentinelCombat),
 		"requirements": nullify(requirements, sentinelReq),
-		"enhancements": nullify(enhancements, sentinelEnh), // always present
+		"enhancements": nullifyKeep(enhancements, sentinelEnh), // ALWAYS inserts a row
 		"ratings":      nullify(ratings, sentinelRating),
 		"spells":       spellRows,
 	}
@@ -334,8 +334,21 @@ func nullify(m map[string]any, isSentinel func(any) bool) map[string]any {
 		}
 	}
 	if !any_ {
-		// caller distinguishes; combat/req/ratings skip (nil), enhancements keeps.
-		return nil
+		return nil // combat/req/ratings: skip the insert when all-sentinel
+	}
+	return out
+}
+
+// nullifyKeep is like nullify but ALWAYS returns the map (for item_enhancements,
+// which inserts a row even when every value is NULL).
+func nullifyKeep(m map[string]any, isSentinel func(any) bool) map[string]any {
+	out := make(map[string]any, len(m))
+	for k, v := range m {
+		if isSentinel(v) {
+			out[k] = nil
+		} else {
+			out[k] = v
+		}
 	}
 	return out
 }