Add proxy functionality. Re-enable local conf.

[rpiaggio]

The UI needs to connect to a second server, which provides an API to connect directly to Navigate's DB.

We can either:

1. Open the server's port to the world.
2. Deploy static files through an nginx server, and configure it as a proxy to both servers.
3. Have the existing server act as a proxy to the other server.

This PR implements option #3. Requests made to /db/* will be forwarded to the other server, stripping /db. The other server's base URI is configurable in app.conf.

Additionally, it reinstantes correctly reading app.conf from resources in development. This was broken when I implemented packaging.

[codecov-commenter]

Codecov Report

Attention: 32 lines in your changes are missing coverage. Please review.

Comparison is base (0cb8679) 28.39% compared to head (45e9ff4) 27.71%.

Files	Patch %	Lines
...navigate/web/server/http4s/WebServerLauncher.scala	0.00%	20 Missing ⚠️
...cala/navigate/web/server/http4s/ProxyBuilder.scala	0.00%	12 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #494      +/-   ##
==========================================
- Coverage   28.39%   27.71%   -0.69%     
==========================================
  Files          47       48       +1     
  Lines        1222     1252      +30     
  Branches        6        7       +1     
==========================================
  Hits          347      347              
- Misses        875      905      +30     

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[jluhrs]

LGTM