feat: Anti-Fake-Evidence System (Phase 1-4b)

Implement full evidence integrity pipeline to prevent compliance theater:
- Confidence levels (E0-E4), truth status tracking, assertion engine
- Four-Eyes approval workflow, audit trail, reject endpoint
- Evidence distribution dashboard, LLM audit routes
- Traceability matrix (backend endpoint + Compliance Hub UI tab)
- Anti-fake badges, control status machine, normative patterns
- 2 migrations, 4 test suites, MkDocs documentation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend-compliance/migrations/077_anti_fake_evidence_phase2.sql

@@ -0,0 +1,37 @@
+-- Migration 077: Anti-Fake-Evidence Phase 2
+-- Assertions table, Four-Eyes columns on Evidence, Audit-Trail performance index
+
+-- 1A. Assertions table
+CREATE TABLE IF NOT EXISTS compliance_assertions (
+    id              VARCHAR(36) PRIMARY KEY DEFAULT gen_random_uuid()::text,
+    tenant_id       VARCHAR(36),
+    entity_type     VARCHAR(50) NOT NULL,
+    entity_id       VARCHAR(36) NOT NULL,
+    sentence_text   TEXT NOT NULL,
+    sentence_index  INTEGER NOT NULL DEFAULT 0,
+    assertion_type  VARCHAR(20) NOT NULL DEFAULT 'assertion',
+    evidence_ids    JSONB DEFAULT '[]'::jsonb,
+    confidence      FLOAT DEFAULT 0.0,
+    normative_tier  VARCHAR(20),
+    verified_by     VARCHAR(200),
+    verified_at     TIMESTAMPTZ,
+    created_at      TIMESTAMPTZ DEFAULT NOW(),
+    updated_at      TIMESTAMPTZ DEFAULT NOW()
+);
+CREATE INDEX IF NOT EXISTS ix_assertion_entity ON compliance_assertions (entity_type, entity_id);
+CREATE INDEX IF NOT EXISTS ix_assertion_type ON compliance_assertions (assertion_type);
+CREATE INDEX IF NOT EXISTS ix_assertion_tenant ON compliance_assertions (tenant_id);
+
+-- 1B. Four-Eyes columns on Evidence
+ALTER TABLE compliance_evidence
+    ADD COLUMN IF NOT EXISTS approval_status VARCHAR(30) DEFAULT 'none',
+    ADD COLUMN IF NOT EXISTS first_reviewer VARCHAR(200),
+    ADD COLUMN IF NOT EXISTS first_reviewed_at TIMESTAMPTZ,
+    ADD COLUMN IF NOT EXISTS second_reviewer VARCHAR(200),
+    ADD COLUMN IF NOT EXISTS second_reviewed_at TIMESTAMPTZ,
+    ADD COLUMN IF NOT EXISTS requires_four_eyes BOOLEAN DEFAULT FALSE;
+CREATE INDEX IF NOT EXISTS ix_evidence_approval_status ON compliance_evidence (approval_status);
+
+-- 1C. Audit-Trail performance index
+CREATE INDEX IF NOT EXISTS ix_audit_trail_entity_action
+    ON compliance_audit_trail (entity_type, action, performed_at);