feat: i18n full support, responsive UI, multi-model AI config, and bug fixes

Major Features:
- Internationalization (i18n) with auto-detection for ES/EN/PT
- Mobile-first responsive design for Studio and Experience
- Multi-model AI configuration (llama3.2:3b, qwen3.5:9b, gpt-oss:latest)
- Course language configuration (auto-detect or fixed per course)

Backend Changes:
- shared/common: ModelType enum for intelligent model selection
- LMS: log_ai_usage function migration (fix chat tutor 500 error)
- LMS/CMS: course language config fields (language_setting, fixed_language)
- LMS: /courses/{id}/language-config endpoint for language detection

Frontend Changes:
- Experience: Enhanced i18n with browser language detection
- Experience: Audio recording with HTTPS check and error handling
- Studio: Memory game with unique pair IDs and debug logging
- Studio: Expanded translations (250+ keys for ES, EN, PT)
- Both: Language selector in headers (mobile responsive)

Documentation:
- AI_MODELS_CONFIG.md: Multi-model configuration guide
- RESPONSIVIDAD_GUIA.md: Mobile-first design patterns
- I18N_RESPONSIVIDAD_IMPLEMENTACION.md: Implementation details
- DEBUG_AUDIO_RECORDING.md: Audio troubleshooting guide
- DEBUG_MEMORY_GAME.md: Memory game debugging steps

Bug Fixes:
- Fix chat tutor 500 error (missing log_ai_usage function)
- Fix audio recording (HTTPS check, browser compatibility)
- Fix memory game pair IDs (unique ID generation)
- Fix HotspotBlock TypeScript errors

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

services/lms-service/src/handlers_embeddings.rs

@@ -8,7 +8,6 @@ use axum::{
 };
 use common::ai::{self, generate_embedding};
 use common::middleware::Org;
-use reqwest::Client;
 use serde::{Deserialize, Serialize};
 use sqlx::PgPool;
 use uuid::Uuid;
@@ -76,7 +75,7 @@ pub async fn generate_knowledge_embeddings(
     .await
     .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;
     
-    let total = entries.len();
+    let _total = entries.len();
     let mut processed = 0;
     let mut failed = 0;
     
@@ -234,12 +233,12 @@ pub async fn semantic_search_knowledge(
     
     let mut param_idx = 3;
     
-    if let Some(course_id) = filters.course_id {
+    if let Some(_course_id) = filters.course_id {
         param_idx += 1;
         query.push_str(&format!(" AND course_id = ${}", param_idx));
     }
     
-    if let Some(lesson_id) = filters.lesson_id {
+    if let Some(_lesson_id) = filters.lesson_id {
         param_idx += 1;
         query.push_str(&format!(" AND lesson_id = ${}", param_idx));
     }