WEB-49: restore Prisma production audit gate

[JS-mark]

Closes WEB-49

Summary

• override only @prisma/config@6.19.3's vulnerable deepmerge-ts@7.1.5 dependency with patched 8.0.1
• keep Prisma 6 compatibility while matching the fix proposed upstream in fix(deps): bump deepmerge-ts from 7.1.5 to 8.0.1 prisma/orm#30054
• remove the duplicate PR WEB-32: harden CI and release gates #7 CLI test-gate changeset and retain the original PR WEB-33: establish v0.4 policy acceptance baseline #6 release note
• preserve the production audit threshold and all existing CI/release gates

Verification

• pnpm install --frozen-lockfile
• pnpm audit:prod — exit 0; 0 high (2 low, 4 moderate remain below the configured gate)
• pnpm turbo run build test typecheck lint --force — 30/30 tasks passed
• pnpm --filter @bridgent/source-prisma test — 10 files, 49 tests passed
• readonly and writes Prisma examples — generate, migrate, and seed passed against disposable SQLite databases
• MCP stdio smoke — readonly exposed 15 tools and no writes; writes exposed 19 tools including exactly the four configured write tools; both returned seeded users
• pnpm changeset status — one @bridgent/cli patch note remains
• pnpm changeset status --since=origin/main
• git diff --check

No audit ignore, threshold reduction, real credential, Prisma major upgrade, or release action is included.