deps: bump prisma 5.4.1 → 6.19.3 (nix build fix)

Required to keep the nix package buildable: nixpkgs unstable no longer
ships prisma-engines 5.x — the unsuffixed `prisma-engines` attr now
aliases 7.x (no libquery_engine.node), and the only versioned attrs are
`prisma-engines_6` (6.19.3) and `prisma-engines_7`. Bump both
`@prisma/client` and `prisma` to ^6.19.0 so the client matches the only
engine we can pin to.

Also:
- package.nix takes `prisma-engines_6` directly. flake.nix passes
  `pkgs.prisma-engines_6 or pkgs.prisma-engines` so the package still
  builds on nixos-25.05 (where prisma-engines is 6.7.0 unsuffixed).
- Drop PRISMA_INTROSPECTION_ENGINE_BINARY — prisma 6 collapsed the
  introspection engine into schema-engine, the binary no longer ships.

Schema is unchanged so existing fresh installs migrate identically.
Existing dev instances with a prisma_5-tracked _prisma_migrations table
will need a one-time `prisma migrate resolve` step on first boot under
the new client; deploy targets are all fresh installs.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

package.nix

@@ -4,7 +4,11 @@
   pnpm_9,
   nodejs_20,
   makeWrapper,
-  prisma-engines,
+  # Pin to prisma-engines_6 (6.19.3) — package.json's `@prisma/client` +
+  # `prisma` are at ^6.19.0. The unversioned `prisma-engines` attr is now
+  # 7.x in nixpkgs which doesn't ship libquery_engine.node, so we'd fail
+  # at postinstall.
+  prisma-engines_6,
   openssl,
   sqlite,
   python311,
@@ -13,6 +17,8 @@
 }:
 
 let
+  prisma-engines = prisma-engines_6;
+
   # The NDK 2.8.1 → 3.0.3 bump (commit 041f431) regenerated pnpm-lock.yaml
   # at lockfile v9 and pinned NDK as `"3.0.3"`. Lockfile + manifest agree
   # post-bump, so the historical patch-back-to-caret-form is no longer
@@ -25,7 +31,10 @@ let
     PRISMA_SCHEMA_ENGINE_BINARY = lib.getExe' prisma-engines "schema-engine";
     PRISMA_QUERY_ENGINE_BINARY = lib.getExe' prisma-engines "query-engine";
     PRISMA_QUERY_ENGINE_LIBRARY = "${prisma-engines}/lib/libquery_engine.node";
-    PRISMA_INTROSPECTION_ENGINE_BINARY = lib.getExe' prisma-engines "introspection-engine";
+    # Prisma 6 collapsed introspection-engine into schema-engine — the
+    # binary no longer ships in prisma-engines_6. The env var is still
+    # honored if present (drops gracefully), but pointing it at a path
+    # that doesn't exist would fail at startup.
     PRISMA_FMT_BINARY = lib.getExe' prisma-engines "prisma-fmt";
     PRISMA_CLIENT_ENGINE_TYPE = "binary";
   };
@@ -40,7 +49,7 @@ stdenv.mkDerivation (finalAttrs: {
     inherit (finalAttrs) pname version src;
     fetcherVersion = 2;
     prePnpmInstall = patchNdk;
-    hash = "sha256-nmjZ2oTw8K4lTA+2gdtWXX7TnM0n39OwvbwG3DBQ9WU=";
+    hash = "sha256-DkFzzsQTuptRR8+rWfr9RGC+5XjSQrZlsZtspWfBW8w=";
   };
 
   postPatch = patchNdk;