docs: define organization account model

docs/product/vision.md

@@ -8,7 +8,7 @@ Active
 
 `Socialize` is a workflow application for social media content review, revision, approval, and publication readiness.
 
-It is not a public social network. It is a workspace-based coordination tool for internal teams, providers, and client approvers.
+It is not a public social network. It is an organization-owned, workspace-based coordination tool for internal teams, providers, and client approvers.
 
 ## Problem
 
@@ -38,8 +38,11 @@ Provide one system of workflow for drafting, revising, reviewing, approving, and
 
 ## Core Product Shape
 
-- workspace-based account boundary
-- agencies able to manage multiple workspaces
+- organizations as the SaaS account, billing, subscription, and connector boundary
+- workspaces as brand/client workflow boundaries owned by one organization
+- agencies, in-house teams, and professional businesses able to manage multiple workspaces
+- organization members able to inherit access across owned workspaces
+- external collaborators able to access specific workspaces without organization membership
 - content items as the main reviewable unit
 - assets and revisions tracked against content items
 - comments and approvals attached to the work itself
@@ -60,7 +63,7 @@ Provide one system of workflow for drafting, revising, reviewing, approving, and
 - not a full publishing engine in version 1
 - not a full DAM platform in version 1
 - not a full analytics product in version 1
-- not a billing/subscription product in version 1
+- not a full billing provider or pricing/package automation product in version 1
 
 ## MVP Scope
 
@@ -86,7 +89,7 @@ Version 1 should focus on approval workflow rather than direct publishing.
 - direct social publishing
 - advanced third-party synchronization
 - analytics suite
-- customer billing flows
+- full customer billing provider integration and pricing/package automation
 
 ## Current Strategic Assumptions