Require AdaMaps API keys via env (no inline default)

Ingest and read keys are now read from environment variables
instead of inline defaults. Validators hard-fail at boot if either
env var is unset.

README.md

@@ -41,7 +41,7 @@ Config file: `/data/adacam/config.json`
 ```json
 {
   "device_id": "auto-generated UUID",
-  "adamaps_key": "***REMOVED***",
+  "adamaps_key": "<your-adamaps-ingest-key>",
   "adamaps_api": "https://api.adamaps.org",
   "ap_interface": "wlp1s0f0",
   "tunnel_host": "",

adacam_api/config.py

@@ -8,7 +8,7 @@ FIRMWARE_VERSION = "adacam-1.0.0"
 
 _defaults = {
     "device_id": None,
-    "adamaps_key": "***REMOVED***",
+    "adamaps_key": "",
     "adamaps_api": "https://api.adamaps.org",
     "ap_interface": "wlp1s0f0",
     "tunnel_host": "",