Add data export functionality with gzip compression

- Add FindByUserID method to HabitEntryRepository (JOIN with habits)
- Implement ExportUserDataHandler to export all user data
- Add GET /api/v1/export endpoint with gzip compression
- Apply strict rate limiting (1 export per hour per user)
- Export includes all habits (active + archived) and entries
- Add i18n translations for export errors (en/es)
- Update all test mocks to implement new repository method
- Export format: JSON with gzip (~10x compression ratio)

internal/infrastructure/http/export_handlers.go

@@ -0,0 +1,65 @@
+package http
+
+import (
+	"compress/gzip"
+	"encoding/json"
+	"net/http"
+
+	"apocapoc-api/internal/application/queries"
+	"apocapoc-api/internal/i18n"
+)
+
+type ExportHandlers struct {
+	exportHandler *queries.ExportUserDataHandler
+	translator    *i18n.Translator
+}
+
+func NewExportHandlers(
+	exportHandler *queries.ExportUserDataHandler,
+	translator *i18n.Translator,
+) *ExportHandlers {
+	return &ExportHandlers{
+		exportHandler: exportHandler,
+		translator:    translator,
+	}
+}
+
+// ExportData godoc
+// @Summary Export user data
+// @Description Export all user habits and entries in JSON format with gzip compression. Limited to 1 export per hour.
+// @Tags export
+// @Security BearerAuth
+// @Produce json
+// @Success 200 {object} queries.ExportUserDataResult "Compressed JSON export"
+// @Failure 401 {object} ErrorResponse "Unauthorized"
+// @Failure 429 {object} ErrorResponse "Rate limit exceeded"
+// @Failure 500 {object} ErrorResponse "Internal server error"
+// @Router /export [get]
+func (h *ExportHandlers) ExportData(w http.ResponseWriter, r *http.Request) {
+	userID := r.Context().Value("user_id").(string)
+
+	query := queries.ExportUserDataQuery{
+		UserID: userID,
+	}
+
+	result, err := h.exportHandler.Handle(r.Context(), query)
+	if err != nil {
+		respondErrorI18n(w, r, h.translator, http.StatusInternalServerError, "export_failed")
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set("Content-Encoding", "gzip")
+	w.Header().Set("Content-Disposition", "attachment; filename=\"apocapoc-export.json.gz\"")
+	w.WriteHeader(http.StatusOK)
+
+	gzipWriter := gzip.NewWriter(w)
+	defer gzipWriter.Close()
+
+	encoder := json.NewEncoder(gzipWriter)
+	encoder.SetIndent("", "  ")
+
+	if err := encoder.Encode(result); err != nil {
+		return
+	}
+}

internal/infrastructure/http/integration_test.go

@@ -58,6 +58,7 @@ func setupTestServer(t *testing.T) *TestServer {
 	getHabitByIDHandler := queries.NewGetHabitByIDHandler(habitRepo)
 	getHabitEntriesHandler := queries.NewGetHabitEntriesHandler(habitRepo, entryRepo)
 	getHabitStatsHandler := queries.NewGetHabitStatsHandler(habitRepo, entryRepo)
+	exportUserDataHandler := queries.NewExportUserDataHandler(habitRepo, entryRepo)
 	updateHandler := commands.NewUpdateHabitHandler(habitRepo)
 	archiveHandler := commands.NewArchiveHabitHandler(habitRepo)
 	markHandler := commands.NewMarkHabitHandler(entryRepo, habitRepo)
@@ -74,8 +75,9 @@ func setupTestServer(t *testing.T) *TestServer {
 	statsHandlers := NewStatsHandlers(getHabitStatsHandler, translator)
 	healthHandlers := NewHealthHandlers(db, nil)
 	userHandlers := NewUserHandlers(deleteUserHandler, translator)
+	exportHandlers := NewExportHandlers(exportUserDataHandler, translator)
 
-	router := NewRouter("http://localhost:3000", habitHandlers, authHandlers, statsHandlers, healthHandlers, userHandlers, jwtService, translator)
+	router := NewRouter("http://localhost:3000", habitHandlers, authHandlers, statsHandlers, healthHandlers, userHandlers, exportHandlers, jwtService, translator)
 
 	handler := http.Handler(router)
 	return &TestServer{

internal/infrastructure/http/router.go

@@ -16,7 +16,7 @@ import (
 	_ "apocapoc-api/docs"
 )
 
-func NewRouter(appURL string, habitHandlers *HabitHandlers, authHandlers *AuthHandlers, statsHandlers *StatsHandlers, healthHandlers *HealthHandlers, userHandlers *UserHandlers, jwtService *auth.JWTService, translator *i18n.Translator) *chi.Mux {
+func NewRouter(appURL string, habitHandlers *HabitHandlers, authHandlers *AuthHandlers, statsHandlers *StatsHandlers, healthHandlers *HealthHandlers, userHandlers *UserHandlers, exportHandlers *ExportHandlers, jwtService *auth.JWTService, translator *i18n.Translator) *chi.Mux {
 	r := chi.NewRouter()
 
 	r.Use(middleware.Logger)
@@ -77,5 +77,11 @@ func NewRouter(appURL string, habitHandlers *HabitHandlers, authHandlers *AuthHa
 		r.Delete("/me", userHandlers.DeleteAccount)
 	})
 
+	r.Route("/api/v1/export", func(r chi.Router) {
+		r.Use(AuthMiddleware(jwtService))
+		r.Use(RateLimitByUser(jwtService, 1, 1*time.Hour))
+		r.Get("/", exportHandlers.ExportData)
+	})
+
 	return r
 }

internal/infrastructure/persistence/sqlite/habit_entry_repository.go

@@ -185,6 +185,24 @@ func (r *HabitEntryRepository) FindByHabitID(ctx context.Context, habitID string
 	return r.scanEntries(rows)
 }
 
+func (r *HabitEntryRepository) FindByUserID(ctx context.Context, userID string) ([]*entities.HabitEntry, error) {
+	query := `
+		SELECT he.id, he.habit_id, he.scheduled_date, he.completed_at, he.value
+		FROM habit_entries he
+		INNER JOIN habits h ON he.habit_id = h.id
+		WHERE h.user_id = ?
+		ORDER BY he.scheduled_date DESC
+	`
+
+	rows, err := r.db.QueryContext(ctx, query, userID)
+	if err != nil {
+		return nil, fmt.Errorf("failed to find entries: %w", err)
+	}
+	defer rows.Close()
+
+	return r.scanEntries(rows)
+}
+
 func (r *HabitEntryRepository) FindPendingByHabitID(ctx context.Context, habitID string, beforeDate time.Time) ([]*entities.HabitEntry, error) {
 	query := `
 		SELECT id, habit_id, scheduled_date, completed_at, value