feat: add resend capability for platform and account invite codes

Revoke-and-recreate flow for both invite systems with email delivery
via Resend API. Includes account invite email template and audit logging.

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

backend/app/api/endpoints/invite.py

@@ -1,4 +1,4 @@
-from datetime import datetime, timezone
+from datetime import datetime, timezone, timedelta
 from typing import Annotated
 from fastapi import APIRouter, Depends, HTTPException, status, Request
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -101,6 +101,91 @@ async def revoke_invite_code(
     await db.commit()
 
 
+@router.post("/{code}/resend", response_model=InviteCodeResponse)
+async def resend_invite_code(
+    code: str,
+    current_user: Annotated[User, Depends(require_admin)],
+    db: Annotated[AsyncSession, Depends(get_db)]
+):
+    """Revoke an existing invite code and create a new one with the same properties, then email it."""
+    result = await db.execute(
+        select(InviteCode).where(InviteCode.code == code)
+    )
+    old_invite = result.scalar_one_or_none()
+
+    if not old_invite:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Invite code not found"
+        )
+
+    if old_invite.is_used:
+        raise HTTPException(
+            status_code=status.HTTP_409_CONFLICT,
+            detail="Cannot resend a used invite code"
+        )
+
+    if not old_invite.email:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Cannot resend an invite code without a recipient email"
+        )
+
+    # Recalculate expiration from now if the old one had an expiration
+    new_expires_at = None
+    if old_invite.expires_at and old_invite.created_at:
+        original_duration = old_invite.expires_at - old_invite.created_at
+        new_expires_at = datetime.now(timezone.utc) + original_duration
+    elif old_invite.expires_at:
+        new_expires_at = old_invite.expires_at
+
+    # Capture properties before deleting
+    email = old_invite.email
+    assigned_plan = old_invite.assigned_plan
+    trial_duration_days = old_invite.trial_duration_days
+    note = old_invite.note
+    old_code = old_invite.code
+
+    await db.delete(old_invite)
+    await db.flush()
+
+    # Create new invite with same properties
+    new_invite = InviteCode(
+        created_by_id=current_user.id,
+        expires_at=new_expires_at,
+        note=note,
+        email=email,
+        assigned_plan=assigned_plan,
+        trial_duration_days=trial_duration_days,
+    )
+    db.add(new_invite)
+    await db.flush()
+
+    # Send email
+    email_sent = await EmailService.send_invite_email(
+        to_email=email,
+        code=new_invite.code,
+        plan=assigned_plan,
+        trial_days=trial_duration_days,
+    )
+    if email_sent:
+        new_invite.email_sent_at = datetime.now(timezone.utc)
+
+    await log_audit(
+        db, current_user.id, "invite.resend", "invite_code", new_invite.id,
+        {
+            "old_code": old_code,
+            "new_code": new_invite.code,
+            "email": email,
+            "email_sent": email_sent,
+        },
+    )
+    await db.commit()
+    await db.refresh(new_invite)
+
+    return new_invite
+
+
 @router.get("/validate/{code}", response_model=InviteCodeValidation)
 @limiter.limit("5/minute")
 async def validate_invite_code(