Add example env files and fixup setup instructions

.env.example

@@ -0,0 +1,44 @@
+# Key used to sign tokens. Generate this with `go run . generate key`
+HMAC_KEY=
+
+# PostgreSQL connection URL (postgresql://user:pass@host:port/dbname)
+DATABASE_URL=
+
+# Redis connection URL (redis://user:pass@host:port)
+REDIS=
+
+# Port for the backend to listen on; frontend assumes this will be 8080 for dev
+PORT=8080
+
+# Frontend base URL, used to construct URLs that point back to the frontend
+BASE_URL=http://localhost:5173
+
+# S3/MinIO configuration, required for avatars, pride flags, and data exports
+# Note: MINIO_ENDPOINT must be set and look like a minio endpoint, but doesn't
+# have to actually point to one you have access to
+MINIO_ENDPOINT=example.com
+MINIO_BUCKET=
+MINIO_ACCESS_KEY_ID=
+MINIO_ACCESS_KEY_SECRET=
+MINIO_SSL=
+
+# IP address of the frontend; requests from here will never be ratelimited
+FRONTEND_IP=
+
+# Auth providers - fill in OAuth app info to enable OAuth login for each
+
+# https://discord.com/developers/applications
+DISCORD_CLIENT_ID=
+DISCORD_CLIENT_SECRET=
+
+# https://developers.google.com/identity/protocols/oauth2#basicsteps
+GOOGLE_CLIENT_ID=
+GOOGLE_CLIENT_SECRET=
+
+# https://www.tumblr.com/oauth/apps
+TUMBLR_CLIENT_ID=
+TUMBLR_CLIENT_SECRET=
+
+# Discord bot config - provide the app's public key in addition to client ID/
+# secret from above to let the bot to respond to command interactions over HTTP
+DISCORD_PUBLIC_KEY=