docs: establish FraudShield constitution v1.0.0

6 core principles: Security-First, Explainability, Test-First,
Observability, Data Privacy by Design, Simplicity (YAGNI).
Includes Security & Compliance, Development Workflow, and Governance sections.

.specify/init-options.json

@@ -0,0 +1,9 @@
+{
+  "ai": "opencode",
+  "branch_numbering": "sequential",
+  "context_file": "AGENTS.md",
+  "here": true,
+  "integration": "opencode",
+  "script": "sh",
+  "speckit_version": "0.8.8"
+}