Security fixes: P0-P2 complete (22 fixes)

P0 (7): Auth-bypass removed, migrations fixed, plugin-upload disabled, RLS FORCE+WITH CHECK, plugin double-registration fixed, persistent volume, domain removed
P1 (11): User/tenant model, Redis centralized, worker separated, transactional outbox, XSS fixed, DMS chunked streaming, permissions unified, password reset, metrics secured, config/docs fixed, cross-tenant FK
P2 (4): Contact model normalized, cross-imports reduced 94%, commands+state machines for contacts/dms/mail/calendar, SPA path-traversal

8 new migrations, 99 unit tests, 13 commands, 8 contracts, 72 files changed

app/schemas/auth.py

@@ -8,6 +8,7 @@ from pydantic import BaseModel, EmailStr, Field
 class LoginRequest(BaseModel):
     email: EmailStr = Field(..., examples=["admin@leocrm.local"])
     password: str = Field(..., min_length=1, examples=["secure-password"])
+    tenant_slug: str | None = Field(None, description="Tenant slug to select tenant at login", examples=["tenant-a"])
 
 
 class PasswordResetRequest(BaseModel):