test(coverage): enforce API and app floors

Measure untouched mobile source, add regression coverage for native media paths and account operations, and enforce ratcheting API and mobile thresholds in required CI checks.

package.json

@@ -19,6 +19,7 @@
     "lint": "turbo lint && npm run lint:harness",
     "lint:harness": "node scripts/lint-harness.mjs",
     "test": "turbo test --filter=!@sauci/e2e",
+    "test:coverage": "npm run test:coverage -w @sauci/api && npm run test:coverage -w @sauci/mobile",
     "test:supabase": "scripts/test-supabase.sh",
     "test:api:integration": "scripts/test-api-integration.sh",
     "test:mobile:e2e": "maestro test e2e/maestro",