fix(#364): add build-shared step to API pipeline

The lint and typecheck steps fail because @mosaic/shared isn't built.
Add a build-shared step that compiles the shared package before lint
and typecheck run, both of which now depend on build-shared in
addition to prisma-generate.

Fixes #364

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

.woodpecker/api.yml

@@ -60,6 +60,7 @@ steps:
       - pnpm --filter "@mosaic/api" lint
     depends_on:
       - prisma-generate
+      - build-shared
 
   prisma-generate:
     image: *node_image
@@ -71,6 +72,16 @@ steps:
     depends_on:
       - install
 
+  build-shared:
+    image: *node_image
+    environment:
+      SKIP_ENV_VALIDATION: "true"
+    commands:
+      - *use_deps
+      - pnpm --filter "@mosaic/shared" build
+    depends_on:
+      - install
+
   typecheck:
     image: *node_image
     environment:
@@ -80,6 +91,7 @@ steps:
       - pnpm --filter "@mosaic/api" typecheck
     depends_on:
       - prisma-generate
+      - build-shared
 
   prisma-migrate:
     image: *node_image