feat: add ?lang=en support to API with default ru

Language Support:
- Create GetLanguage() helper function
- Support both 'lang' and 'language' query parameters
- Convert short codes (en/ru) to TMDB format (en-US/ru-RU)
- Default language: ru-RU

Changes:
- pkg/handlers/lang_helper.go: new helper for language detection
- pkg/handlers/movie.go: use GetLanguage() in all endpoints
- pkg/handlers/tv.go: use GetLanguage() in all endpoints

How to use:
- ?lang=en → returns English content
- ?lang=ru → returns Russian content (default)
- No param → defaults to Russian

All movie/TV endpoints now support multilingual content:
GET /api/v1/movies/{id}?lang=en
GET /api/v1/movies/popular?lang=en
GET /api/v1/tv/{id}?lang=en
etc.

pkg/handlers/lang_helper.go

@@ -0,0 +1,35 @@
+package handlers
+
+import (
+	"net/http"
+)
+
+// GetLanguage extracts the lang parameter from request and returns it with default "ru"
+// Supports both "lang" and "language" query parameters
+// Valid values: "ru", "en"
+// Default: "ru"
+func GetLanguage(r *http.Request) string {
+	// Check "lang" parameter first (our new standard)
+	lang := r.URL.Query().Get("lang")
+	
+	// Fall back to "language" for backward compatibility
+	if lang == "" {
+		lang = r.URL.Query().Get("language")
+	}
+	
+	// Default to "ru" if not specified
+	if lang == "" {
+		return "ru-RU"
+	}
+	
+	// Convert short codes to TMDB format
+	switch lang {
+	case "en":
+		return "en-US"
+	case "ru":
+		return "ru-RU"
+	default:
+		// Return as-is if already in correct format
+		return lang
+	}
+}

pkg/handlers/movie.go

@@ -29,7 +29,7 @@ func (h *MovieHandler) Search(w http.ResponseWriter, r *http.Request) {
 	}
 
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 	region := r.URL.Query().Get("region")
 	year := getIntQuery(r, "year", 0)
 
@@ -54,7 +54,7 @@ func (h *MovieHandler) GetByID(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 
 	movie, err := h.movieService.GetByID(id, language)
 	if err != nil {
@@ -71,7 +71,7 @@ func (h *MovieHandler) GetByID(w http.ResponseWriter, r *http.Request) {
 
 func (h *MovieHandler) Popular(w http.ResponseWriter, r *http.Request) {
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 	region := r.URL.Query().Get("region")
 
 	movies, err := h.movieService.GetPopular(page, language, region)
@@ -89,7 +89,7 @@ func (h *MovieHandler) Popular(w http.ResponseWriter, r *http.Request) {
 
 func (h *MovieHandler) TopRated(w http.ResponseWriter, r *http.Request) {
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 	region := r.URL.Query().Get("region")
 
 	movies, err := h.movieService.GetTopRated(page, language, region)
@@ -107,7 +107,7 @@ func (h *MovieHandler) TopRated(w http.ResponseWriter, r *http.Request) {
 
 func (h *MovieHandler) Upcoming(w http.ResponseWriter, r *http.Request) {
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 	region := r.URL.Query().Get("region")
 
 	movies, err := h.movieService.GetUpcoming(page, language, region)
@@ -125,7 +125,7 @@ func (h *MovieHandler) Upcoming(w http.ResponseWriter, r *http.Request) {
 
 func (h *MovieHandler) NowPlaying(w http.ResponseWriter, r *http.Request) {
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 	region := r.URL.Query().Get("region")
 
 	movies, err := h.movieService.GetNowPlaying(page, language, region)
@@ -150,7 +150,7 @@ func (h *MovieHandler) GetRecommendations(w http.ResponseWriter, r *http.Request
 	}
 
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 
 	movies, err := h.movieService.GetRecommendations(id, page, language)
 	if err != nil {
@@ -174,7 +174,7 @@ func (h *MovieHandler) GetSimilar(w http.ResponseWriter, r *http.Request) {
 	}
 
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 
 	movies, err := h.movieService.GetSimilar(id, page, language)
 	if err != nil {

pkg/handlers/tv.go

@@ -29,7 +29,7 @@ func (h *TVHandler) Search(w http.ResponseWriter, r *http.Request) {
 	}
 
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 	year := getIntQuery(r, "first_air_date_year", 0)
 
 	tvShows, err := h.tvService.Search(query, page, language, year)
@@ -53,7 +53,7 @@ func (h *TVHandler) GetByID(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 
 	tvShow, err := h.tvService.GetByID(id, language)
 	if err != nil {
@@ -70,7 +70,7 @@ func (h *TVHandler) GetByID(w http.ResponseWriter, r *http.Request) {
 
 func (h *TVHandler) Popular(w http.ResponseWriter, r *http.Request) {
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 
 	tvShows, err := h.tvService.GetPopular(page, language)
 	if err != nil {
@@ -87,7 +87,7 @@ func (h *TVHandler) Popular(w http.ResponseWriter, r *http.Request) {
 
 func (h *TVHandler) TopRated(w http.ResponseWriter, r *http.Request) {
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 
 	tvShows, err := h.tvService.GetTopRated(page, language)
 	if err != nil {
@@ -104,7 +104,7 @@ func (h *TVHandler) TopRated(w http.ResponseWriter, r *http.Request) {
 
 func (h *TVHandler) OnTheAir(w http.ResponseWriter, r *http.Request) {
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 
 	tvShows, err := h.tvService.GetOnTheAir(page, language)
 	if err != nil {
@@ -121,7 +121,7 @@ func (h *TVHandler) OnTheAir(w http.ResponseWriter, r *http.Request) {
 
 func (h *TVHandler) AiringToday(w http.ResponseWriter, r *http.Request) {
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 
 	tvShows, err := h.tvService.GetAiringToday(page, language)
 	if err != nil {
@@ -145,7 +145,7 @@ func (h *TVHandler) GetRecommendations(w http.ResponseWriter, r *http.Request) {
 	}
 
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 
 	tvShows, err := h.tvService.GetRecommendations(id, page, language)
 	if err != nil {
@@ -169,7 +169,7 @@ func (h *TVHandler) GetSimilar(w http.ResponseWriter, r *http.Request) {
 	}
 
 	page := getIntQuery(r, "page", 1)
-	language := r.URL.Query().Get("language")
+	language := GetLanguage(r)
 
 	tvShows, err := h.tvService.GetSimilar(id, page, language)
 	if err != nil {