Allow admins to add photos to existing reporting proposals

[microstudi]

When managing users proposals, the admin is not able to do much with them, just assign a valuator and respond it.

We want, only for this module "reporting proposals", to allow admins manage the photo gallery of anyone's proposal.

Mockup (it does not necessarily have to be exactly this, maybe borrow the same behavior of an admin editing proposal is fine):

• [x] Override the views
• [x] Reuse/adapt or be inspired by how and admin adds photos to a proposal (from the admin side)
• [x] Tests

[paarals]

we have some specifics requeriments also from client: Acceptance criteria

• [ ] Up to 3 pictures can be added to a proposal in the backend (maximum)
• [x] Additional photos are shown in backend proposal
• [x] (if possible) Additional photos are shown in frontend proposal

[pokecodebot]

make sure of a confirmation modal on deletion