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/migrations/20260320000001_add_log_ai_usage_function.sql

@@ -0,0 +1,67 @@
+-- AI Usage Tracking: Add log_ai_usage function
+-- Required for chat with tutor and other AI features
+
+-- Create ai_usage_logs table if not exists
+CREATE TABLE IF NOT EXISTS ai_usage_logs (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id UUID NOT NULL,
+    organization_id UUID NOT NULL,
+    tokens_used INTEGER NOT NULL,
+    input_tokens INTEGER NOT NULL,
+    output_tokens INTEGER NOT NULL,
+    endpoint VARCHAR(255) NOT NULL,
+    model VARCHAR(100) NOT NULL,
+    request_type VARCHAR(50) NOT NULL,
+    request_metadata JSONB,
+    estimated_cost_usd NUMERIC(10, 6),
+    created_at TIMESTAMPTZ DEFAULT NOW(),
+    prompt TEXT,
+    response TEXT
+);
+
+-- Create indexes for performance
+CREATE INDEX IF NOT EXISTS idx_ai_usage_logs_user_id ON ai_usage_logs(user_id);
+CREATE INDEX IF NOT EXISTS idx_ai_usage_logs_org_id ON ai_usage_logs(organization_id);
+CREATE INDEX IF NOT EXISTS idx_ai_usage_logs_created_at ON ai_usage_logs(created_at);
+CREATE INDEX IF NOT EXISTS idx_ai_usage_logs_endpoint ON ai_usage_logs(endpoint);
+
+-- Create log_ai_usage function
+CREATE OR REPLACE FUNCTION log_ai_usage(
+    p_user_id UUID,
+    p_org_id UUID,
+    p_tokens INTEGER,
+    p_input_tokens INTEGER,
+    p_output_tokens INTEGER,
+    p_endpoint VARCHAR,
+    p_model VARCHAR,
+    p_request_type VARCHAR,
+    p_metadata JSONB,
+    p_prompt TEXT DEFAULT NULL,
+    p_response TEXT DEFAULT NULL
+)
+RETURNS UUID AS $$
+DECLARE
+    v_log_id UUID;
+    v_cost NUMERIC(10, 6);
+BEGIN
+    -- Calculate estimated cost (OpenAI-like pricing)
+    v_cost := (p_input_tokens::NUMERIC * 0.000001) + (p_output_tokens::NUMERIC * 0.000003);
+
+    INSERT INTO ai_usage_logs (
+        user_id, organization_id, tokens_used, input_tokens, output_tokens,
+        endpoint, model, request_type, request_metadata, estimated_cost_usd,
+        prompt, response
+    )
+    VALUES (
+        p_user_id, p_org_id, p_tokens, p_input_tokens, p_output_tokens,
+        p_endpoint, p_model, p_request_type, p_metadata, v_cost,
+        p_prompt, p_response
+    )
+    RETURNING id INTO v_log_id;
+
+    RETURN v_log_id;
+END;
+$$ LANGUAGE plpgsql;
+
+COMMENT ON COLUMN ai_usage_logs.prompt IS 'The actual prompt sent to the AI model';
+COMMENT ON COLUMN ai_usage_logs.response IS 'The AI model response content';

services/lms-service/migrations/20260320000002_add_course_language_config.sql

@@ -0,0 +1,24 @@
+-- Add language configuration to courses table (LMS side)
+-- This mirrors the CMS migration for cross-service compatibility
+
+ALTER TABLE courses 
+ADD COLUMN IF NOT EXISTS language_setting VARCHAR(20) DEFAULT 'auto',
+ADD COLUMN IF NOT EXISTS fixed_language VARCHAR(5) DEFAULT NULL;
+
+-- Add comment explaining the fields
+COMMENT ON COLUMN courses.language_setting IS 'Language mode: auto (detect from user browser) or fixed (use fixed_language)';
+COMMENT ON COLUMN courses.fixed_language IS 'Fixed language code (es, en, pt) when language_setting is fixed. NULL when language_setting is auto.';
+
+-- Add check constraints (only if they don't exist)
+DO $$ BEGIN
+    ALTER TABLE courses ADD CONSTRAINT chk_language_setting CHECK (language_setting IN ('auto', 'fixed'));
+EXCEPTION WHEN duplicate_object THEN null;
+END $$;
+
+DO $$ BEGIN
+    ALTER TABLE courses ADD CONSTRAINT chk_fixed_language CHECK (fixed_language IS NULL OR fixed_language IN ('es', 'en', 'pt'));
+EXCEPTION WHEN duplicate_object THEN null;
+END $$;
+
+-- Create index for filtering courses by language
+CREATE INDEX IF NOT EXISTS idx_courses_language ON courses(language_setting, fixed_language);