feat(capability-requests): add routing dispute & reroute workflow (CUST-WP-0027)

Adds a structured dispute mechanism when capability request routing is wrong:
- New `routing_disputed` status with four DB columns (dispute_reason, disputed_by,
  dispute_suggested_domain, disputed_at) via Alembic migration m0h1i2j3k4l5
- POST /capability-requests/{id}/dispute — any party can flag misrouting with a reason
  and optional suggested domain; notifies custodian + current fulfilling domain
- POST /capability-requests/{id}/reroute — custodian re-routes to correct domain via
  catalog_entry_id or direct slug; appends audit trail to routing_note; resets to requested
- Two new MCP tools: dispute_capability_routing and reroute_capability_request
- Dashboard: amber disputed-banner at top of Summary, routing_disputed Kanban column,
  dispute details (reason, suggested domain, raised-by) shown on disputed cards

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

api/schemas/capability_request.py

@@ -62,6 +62,19 @@ class CapabilityRequestPatch(BaseModel):
     fulfilling_workstream_id: uuid.UUID | None = None
 
 
+class CapabilityRequestDispute(BaseModel):
+    reason: str
+    disputed_by: str
+    suggested_domain: str | None = None
+
+
+class CapabilityRequestReroute(BaseModel):
+    note: str
+    rerouted_by: str
+    domain: str | None = None            # slug — used if catalog_entry_id not given
+    catalog_entry_id: uuid.UUID | None = None  # preferred: re-derives domain
+
+
 class CapabilityRequestRead(BaseModel):
     model_config = ConfigDict(from_attributes=True)
 
@@ -81,6 +94,10 @@ class CapabilityRequestRead(BaseModel):
     catalog_entry_id: uuid.UUID | None = None
     resolution_note: str | None = None
     routing_note: str | None = None
+    dispute_reason: str | None = None
+    disputed_by: str | None = None
+    dispute_suggested_domain: str | None = None
+    disputed_at: datetime | None = None
     accepted_at: datetime | None = None
     completed_at: datetime | None = None
     created_at: datetime