Add local authentication option (#37)

Co-authored-by: Shaun Campbell <shaun@campbellwireless.net>
Reviewed-on: #37
Co-authored-by: AI Agent <ai-agent@campbellwireless.net>
Co-committed-by: AI Agent <ai-agent@campbellwireless.net>

.env.example

@@ -10,6 +10,15 @@ AUTH_URL=https://cloud.campbellwireless.net/trips/auth
 # Auth.js secret — generate with: openssl rand -base64 32
 AUTH_SECRET=
 
+# Local auth
+LOCAL_AUTH_ENABLED=false
+LOCAL_AUTH_ARGON2_MEMORY_KB=65536
+LOCAL_AUTH_ARGON2_TIME_COST=3
+LOCAL_AUTH_ARGON2_PARALLELISM=1
+LOCAL_AUTH_MAX_ATTEMPTS=5
+LOCAL_AUTH_WINDOW_SECONDS=900
+LOCAL_AUTH_LOCKOUT_SECONDS=900
+
 # Admin — comma-separated user IDs (from auth provider) that can access /admin
 ADMIN_USER_IDS=