feat: add email notification service with SMTP support

- Create pkg/email package (sender, templates, types)
- SMTP client with TLS, rate limiting, async sending
- HTML email templates with GooSeek branding
- Integrate welcome + password reset emails in auth-svc
- Add limit warning emails (80%/100%) in llm-svc middleware
- Add space invite endpoint with email notification in thread-svc
- Add GetUserEmail helper in JWT middleware
- Add SMTP config to .env, config.go, K8s configmap

Made-with: Cursor

backend/deploy/k8s/configmap.yaml

@@ -41,6 +41,13 @@ data:
   S3_USE_SSL: "${S3_USE_SSL}"
   S3_REGION: "${S3_REGION}"
   S3_PUBLIC_URL: "${S3_PUBLIC_URL}"
+  SMTP_HOST: "${SMTP_HOST}"
+  SMTP_PORT: "${SMTP_PORT}"
+  SMTP_USER: "${SMTP_USER}"
+  SMTP_FROM: "${SMTP_FROM}"
+  SMTP_TLS: "${SMTP_TLS}"
+  SITE_URL: "https://gooseek.ru"
+  SITE_NAME: "GooSeek"
 ---
 apiVersion: v1
 kind: Secret
@@ -55,5 +62,6 @@ stringData:
   JWT_SECRET: "${JWT_SECRET}"
   TIMEWEB_API_KEY: "${TIMEWEB_API_KEY}"
   OLLAMA_API_TOKEN: "${OLLAMA_API_TOKEN}"
+  SMTP_PASSWORD: "${SMTP_PASSWORD}"
   POSTGRES_USER: "gooseek"
   POSTGRES_PASSWORD: "gooseek"