feat(onboarding): add PATCH /users/me/onboarding-step + dismiss-rest

Persists welcome-wizard Step 1/2/3 progress for self-serve signup Phase 2.
PATCH validates step cannot decrease, ignores `data` on action="skip", and
is idempotent on re-PATCH of the same step. POST /users/me/onboarding-dismiss-rest
backs the wizard's "Skip the rest" button.

Both routes added to _EMAIL_VERIFICATION_ALLOWLIST and _SUBSCRIPTION_GUARD_ALLOWLIST
so the wizard runs before email verification and during the trial. 4 integration
tests cover field writes, skip semantics, decrease guard, and dismiss-rest.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/app/schemas/onboarding.py

@@ -1,4 +1,6 @@
-from pydantic import BaseModel
+from typing import Literal, Optional
+
+from pydantic import BaseModel, Field
 
 
 class OnboardingStatus(BaseModel):
@@ -10,3 +12,40 @@ class OnboardingStatus(BaseModel):
     connected_psa: bool
     is_team_user: bool
     dismissed: bool
+
+
+# --- Welcome wizard (Phase 2) ----------------------------------------------
+
+
+TeamSizeBucket = Literal["1-2", "3-5", "6-10", "11-25", "26+"]
+RoleAtSignup = Literal["owner", "lead_tech", "tech", "other"]
+PrimaryPsa = Literal["connectwise", "autotask", "halopsa", "none"]
+WizardStep = Literal[1, 2, 3]
+WizardAction = Literal["complete", "skip"]
+
+
+class OnboardingStepData(BaseModel):
+    """Optional payload carried with `action="complete"` for steps 1 and 2.
+
+    Step 1 fields: company_name, team_size_bucket, role_at_signup
+    Step 2 fields: primary_psa
+    Step 3 has no data (invitations posted separately).
+    """
+
+    # Step 1
+    company_name: Optional[str] = Field(default=None, max_length=255)
+    team_size_bucket: Optional[TeamSizeBucket] = None
+    role_at_signup: Optional[RoleAtSignup] = None
+    # Step 2
+    primary_psa: Optional[PrimaryPsa] = None
+
+
+class OnboardingStepRequest(BaseModel):
+    step: WizardStep
+    action: WizardAction
+    data: Optional[OnboardingStepData] = None
+
+
+class OnboardingStepResponse(BaseModel):
+    onboarding_step_completed: Optional[int]
+    onboarding_dismissed: bool