feat: user management — admin create, password reset, archive/delete, quick invite

Phase 1: must_change_password enforcement + change password endpoint/page
Phase 2: Admin user creation (M365-style) with temp password
Phase 3: Password reset (self-service forgot + admin-triggered)
Phase 4: User archive (soft delete) + hard delete with precheck
Phase 5: Quick invite from admin Users page

Also fixes:
- Auto-create subscription for accounts missing one
- Hard delete precheck ignores sole-member personal accounts
- Seed script patches tree nodes for validation compliance

Migrations: 031 (must_change_password), 032 (password_reset_tokens), 033 (user soft delete)

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

backend/app/models/password_reset_token.py

@@ -0,0 +1,47 @@
+import uuid
+from datetime import datetime, timezone
+from typing import Optional
+from sqlalchemy import String, DateTime, ForeignKey
+from sqlalchemy.orm import Mapped, mapped_column
+from sqlalchemy.dialects.postgresql import UUID
+from app.core.database import Base
+
+
+class PasswordResetToken(Base):
+    __tablename__ = "password_reset_tokens"
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        primary_key=True,
+        default=uuid.uuid4
+    )
+    token_hash: Mapped[str] = mapped_column(String(64), unique=True, nullable=False, index=True)
+    user_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("users.id"),
+        nullable=False,
+        index=True
+    )
+    expires_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)
+    used_at: Mapped[Optional[datetime]] = mapped_column(DateTime(timezone=True), nullable=True)
+    created_by_admin_id: Mapped[Optional[uuid.UUID]] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("users.id"),
+        nullable=True
+    )
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        default=lambda: datetime.now(timezone.utc)
+    )
+
+    @property
+    def is_used(self) -> bool:
+        return self.used_at is not None
+
+    @property
+    def is_expired(self) -> bool:
+        return datetime.now(timezone.utc) > self.expires_at
+
+    @property
+    def is_valid(self) -> bool:
+        return not self.is_used and not self.is_expired