feat: switch email delivery from Resend to SMTP with libcurl integration

docs/API_SPEC.md

@@ -32,7 +32,7 @@ Authorization: Bearer <token>
 - `POST /auth/register`
   citizen registration without password
 - `POST /auth/otp/request`
-  queues OTP email through configured mail provider
+  sends OTP email through configured SMTP provider
 - `POST /auth/otp/verify`
   consumes OTP, returns bearer token
 - `POST /auth/cie/start`

docs/ARCHITECTURE.md

@@ -24,7 +24,7 @@ generate public read-only intervention links.
 
 ## Runtime Model
 - Auth uses bearer tokens from `api_tokens`.
-- OTP login uses `otp_challenges` and async email delivery through configured mail provider.
+- OTP login uses `otp_challenges` and SMTP email delivery through configured mail provider.
 - CIE login uses external Django RP service:
   - Visione creates local `state`
   - Django RP completes CIE/OIDC and sends signed identity payload to Visione

docs/openapi/visione.openapi.yaml

@@ -2582,7 +2582,7 @@
     },
     "/api/v1/auth/otp/request": {
       "post": {
-        "description": "Queues a one-time code by email through configured mail provider.",
+        "description": "Sends a one-time code by email through configured SMTP provider.",
         "operationId": "AuthController.requestOtp",
         "parameters": [ ],
         "requestBody": {
@@ -3312,7 +3312,7 @@
     },
     "/api/v1/reports": {
       "get": {
-        "description": "Lists reports visible to the authenticated user.",
+        "description": "Lists reports visible to the authenticated user. Citizens see own reports only; operators and admins can read all reports. Admin can use this endpoint for global read-only overview screens.",
         "operationId": "ReportController.list",
         "parameters": [
           {