fix(psa): fix time entry AttributeError and show all users in member mapping

- Fix create_time_entry() using self._client instead of self.client
- GET /member-mappings now returns all active account users, not just mapped
  ones — allows manual assignment when auto-match by email doesn't work
- PsaMemberMappingResponse mapping fields are now Optional (id, external_member_id,
  external_member_name, matched_by) to represent unmapped users
- Frontend MemberMappingTab skips null external_member_id when building
  localMappings, and derives user list from all returned entries
- Add docs/connectwise-psa-testing-checklist.md

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

frontend/src/pages/account/IntegrationsPage.tsx

@@ -648,10 +648,12 @@ function MemberMappingTab({ connection }: { connection: PsaConnectionResponse |
       setCwMembers(members)
       setMappings(existingMappings)
 
-      // Build local mapping state from existing mappings
+      // Build local mapping state from existing mappings (skip unmapped entries)
       const lookup: Record<string, { external_member_id: string; external_member_name: string }> = {}
       for (const m of existingMappings) {
-        lookup[m.user_id] = { external_member_id: m.external_member_id, external_member_name: m.external_member_name }
+        if (m.external_member_id) {
+          lookup[m.user_id] = { external_member_id: m.external_member_id, external_member_name: m.external_member_name ?? '' }
+        }
       }
       setLocalMappings(lookup)
       setIsDirty(false)
@@ -716,14 +718,11 @@ function MemberMappingTab({ connection }: { connection: PsaConnectionResponse |
     }
   }
 
-  // Derive user list from mappings response (all account users are returned)
-  const userRows = mappings.length > 0
+  // All account users — includes both mapped and unmapped
+  const uniqueUsers = hasLoaded
     ? mappings.map(m => ({ user_id: m.user_id, user_email: m.user_email, user_name: m.user_name, matched_by: m.matched_by }))
     : []
 
-  // Deduplicate: mappings may only contain mapped users, so we show what we have
-  const uniqueUsers = hasLoaded ? userRows : []
-
   if (!connection) {
     return (
       <div className="max-w-3xl">

frontend/src/types/integrations.ts

@@ -108,13 +108,13 @@ export interface PsaMemberResponse {
 }
 
 export interface PsaMemberMappingResponse {
-  id: string
+  id: string | null
   user_id: string
   user_email: string
   user_name: string
-  external_member_id: string
-  external_member_name: string
-  matched_by: string
+  external_member_id: string | null
+  external_member_name: string | null
+  matched_by: string | null
 }
 
 export interface AutoMatchResult {