feat: Projects backend slice — auth, primitives, backend, UI (#3)

packages/backend/convex/authz.ts

@@ -11,7 +11,7 @@ export interface AuthContext {
   };
 }
 
-export const requireOwnerId = async (ctx: AuthContext): Promise<string> => {
+export const requireAuthUserId = async (ctx: AuthContext): Promise<string> => {
   const identity = await ctx.auth.getUserIdentity();
   if (!identity) {
     throw new ConvexError("Authentication required");
@@ -28,7 +28,7 @@ export const requireOrganizationMember = async (
   ctx: QueryCtx | MutationCtx,
   organizationId: Id<"organizations">
 ): Promise<string> => {
-  const userId = await requireOwnerId(ctx);
+  const userId = await requireAuthUserId(ctx);
   const membership = await ctx.db
     .query("organizationMembers")
     .withIndex("by_organizationId_and_userId", (q) =>
@@ -40,3 +40,41 @@ export const requireOrganizationMember = async (
   }
   return userId;
 };
+
+/**
+ * Resolve the authenticated user's personal/current organization. Browsers
+ * never submit organization IDs for Project commands; this resolves the
+ * tenant boundary server-side through the authenticated identity.
+ */
+export const requireCurrentOrganization = async (
+  ctx: QueryCtx | MutationCtx
+): Promise<{ organizationId: Id<"organizations">; userId: string }> => {
+  const userId = await requireAuthUserId(ctx);
+  const organization = await ctx.db
+    .query("organizations")
+    .withIndex("by_createdBy_and_kind", (q) =>
+      q.eq("createdBy", userId).eq("kind", "personal")
+    )
+    .unique();
+  if (!organization) {
+    throw new ConvexError("Organization not found");
+  }
+  return { organizationId: organization._id, userId };
+};
+
+/**
+ * Prove the authenticated user is a member of the project's organization.
+ * Projects are organization-scoped; unauthorized single-object operations
+ * throw "Project not found" to avoid leaking existence.
+ */
+export const requireProjectMember = async (
+  ctx: QueryCtx | MutationCtx,
+  projectId: Id<"projects">
+): Promise<{ organizationId: Id<"organizations">; userId: string }> => {
+  const project = await ctx.db.get(projectId);
+  if (!project) {
+    throw new ConvexError("Project not found");
+  }
+  const userId = await requireOrganizationMember(ctx, project.organizationId);
+  return { organizationId: project.organizationId, userId };
+};