feat: self-serve signup Phase 2 (frontend cutover) (#162)

Co-authored-by: Michael Chihlas <michael@resolutionflow.com>
Co-committed-by: Michael Chihlas <michael@resolutionflow.com>

backend/app/schemas/admin.py

@@ -172,6 +172,21 @@ class PlanLimitResponse(BaseModel):
         from_attributes = True
 
 
+class PlanLimitWithBillingResponse(PlanLimitResponse):
+    """PlanLimits + plan_billing fields merged. Billing fields are None when no
+    plan_billing row exists for the plan yet."""
+    display_name: Optional[str] = None
+    description: Optional[str] = None
+    monthly_price_cents: Optional[int] = None
+    annual_price_cents: Optional[int] = None
+    stripe_product_id: Optional[str] = None
+    stripe_monthly_price_id: Optional[str] = None
+    stripe_annual_price_id: Optional[str] = None
+    is_public: Optional[bool] = None
+    is_archived: Optional[bool] = None
+    sort_order: Optional[int] = None
+
+
 class PlanLimitUpdate(BaseModel):
     plan: str
     max_trees: Optional[int] = None
@@ -180,6 +195,19 @@ class PlanLimitUpdate(BaseModel):
     custom_branding: bool = False
     priority_support: bool = False
     export_formats: list = Field(default_factory=lambda: ["markdown", "text"])
+    # plan_billing fields — all optional, partial-update semantics. If any are
+    # set in the body, the admin endpoint upserts the plan_billing row in the
+    # same transaction.
+    display_name: Optional[str] = None
+    description: Optional[str] = None
+    monthly_price_cents: Optional[int] = None
+    annual_price_cents: Optional[int] = None
+    stripe_product_id: Optional[str] = None
+    stripe_monthly_price_id: Optional[str] = None
+    stripe_annual_price_id: Optional[str] = None
+    is_public: Optional[bool] = None
+    is_archived: Optional[bool] = None
+    sort_order: Optional[int] = None
 
 
 class AccountOverrideCreate(BaseModel):