Add cost controls to limit hosting costs

## Limits

Limit | Max | Web | Android | Cloud Functions
-- | -- | -- | -- | --
Max. survery / job / submission size | 1 MiB* |   |   |  
Total no. surveys |   |   |   | ✔️**
No. surveys / user |   | ✔️ |   | ✔️**
No. emails / survey |   | ✔️ |   |  
Survey, job, task name length |   | ✔️ |   |  
Survey description length |   | ✔️ |   |  
No. jobs / survey |   | ✔️ |   |  
No. tasks / job |   | ✔️ |   |  
No. mult. choice options / task |   | ✔️ |   |  
Mult. choice option label length |   | ✔️ |   |  
Custom data consent terms length |   | ✔️ |   |  
No. sites / job |   |   | ✔️ | ✔️**
No. vertices / primary (LOI) polygon |   |   | ✔️ | ✔️
No. vertices / secondary polygon |   |   | ✔️ | ✔️**
Photo size |   |   | ✔️ |  
Short text length | 255 chars |   | ✔️ |  

*[source sheet](http://docs/spreadsheets/d/1IRN6Nf7OFDAvk-__KukBb7PUu-VLjkr4ScKriMPf8aw?gid=0#gid=0)*

\* enforced by Firebase
\*\* create/edit operations will need to moved to Cloud Functions for this path to work

@jo-spek @kenstershiro Let's work through this at our next sync?