fix force_ssl compile-time config mismatch

force_ssl must be set at compile time (in prod.exs), not runtime.
Phoenix validates compile-time config at boot and was crashing
because the value differed between compile and runtime.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

config/prod.exs

@@ -5,7 +5,11 @@ import Config
 # manifest is generated by the `mix assets.deploy` task,
 # which you should run after static files are built and
 # before starting your production server.
-config :berrypod, BerrypodWeb.Endpoint, cache_static_manifest: "priv/static/cache_manifest.json"
+config :berrypod, BerrypodWeb.Endpoint,
+  cache_static_manifest: "priv/static/cache_manifest.json",
+  # HSTS tells browsers to always use HTTPS for this domain (1 year, include subdomains)
+  # This must be set at compile time, not runtime
+  force_ssl: [hsts: true, rewrite_on: [:x_forwarded_proto]]
 
 # Configures Swoosh API Client
 config :swoosh, api_client: Swoosh.ApiClient.Req