Remove need to add all mail template params to view response data. This
was originally intended functionality but the wrong value was passed to
the `deliver` function, and no `data` argument was given, making it
cumbersome to create new values.
Use in-memory KV store (JetKV) for simple job queue.
Build script generates an array of Zig modules in `src/app/jobs/` and
stores their name + run function (`run(allocator, params, logger)`).
View functions schedule jobs with arbitrary params.
Thread pool spawns a (configurable) number of workers and pops jobs from
the queue, then invokes the appropriate run function.
