feat: WeKan ticketing source

- wekan connector: board id as project key, cards assigned to the
  consultant's WeKan username (assignees with member fallback), archived
  cards skipped, client-side modifiedAt since-filtering, username/password
  login with token reuse (or pre-issued token), case-insensitive identity
- fake-WeKan unit tests: factory validation, test-connection, fetch
  filtering, key listing, token reuse
- admin customer wizard: WeKan option + credential fields
- OpenAPI enum + credential shapes, README identity mapping docs

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -1,7 +1,7 @@
 # Bounty Board
 
 A consulting work-management platform: imports tickets from Jira / Azure
-DevOps / YouTrack (or an offline `demo` source), lets **consultants** atomize
+DevOps / YouTrack / WeKan (or an offline `demo` source), lets **consultants** atomize
 them into small developer tasks with AI assistance, publishes them on a
 **bounty board** where **developers** claim work (or an **AI work performer**
 does it), and tracks review, approval, and bounty-based metrics.
@@ -176,7 +176,9 @@ limits, and the mock services' Anthropic settings.
 
 Consultants map their ticketing identities in their profile via
 `users.extra.ticketingIdentities` (e.g. set by an admin):
-`{"jira": "consultant@corp.com", "azure_devops": "consultant@corp.com", "youtrack": "consultant.login"}`.
+`{"jira": "consultant@corp.com", "azure_devops": "consultant@corp.com", "youtrack": "consultant.login", "wekan": "wekan-username"}`.
+For WeKan the customer's project key is the **board id** and cards assigned
+to the consultant (assignees, falling back to members) are imported.
 The `demo` ticketing type needs no identity.
 
 ## Deliberately out of scope (documented stubs, §11.24)