refactor: optimize project structure, migrate to SQLite, and add new features

fix:
  - Fix TypeScript type errors in api-wrapper.ts (ApiResponse type)
  - Fix backward compatibility in database.ts getSettings() for missing fields
  - Fix default value for weekNavigationEnabled (changed from true to false)
  - Fix API routes error handling with unified wrapper
  - Fix duplicate toggle switch code in admin.tsx (6 instances)
  - Fix inconsistent authentication check in API routes (unified with withAuth)
  - Fix error message text in loading-context.tsx (improved user experience)

add:
  - Add database.ts: SQLite database layer with better-sqlite3 for persistent storage
    * Groups management (CRUD operations)
    * Settings management with caching
    * Admin password hashing with bcrypt
    * Automatic database initialization and migration
  - Add api-wrapper.ts utility for unified API route handling
    * withAuth wrapper for protected routes
    * withMethods wrapper for public routes
    * Consistent error handling and method validation
  - Add validation.ts utility with centralized validation functions
    * validateCourse - course validation (1-5)
    * validateGroupId - group ID format validation
    * validatePassword - password strength validation
  - Add showAddGroupButton setting to control visibility of 'Add Group' button on homepage
  - Add toggle switch component in admin.tsx for reusable UI (replaces 6 duplicate instances)
  - Add CourseSelect component in admin.tsx for reusable course selection
  - Add DialogFooterButtons component in admin.tsx for reusable dialog footer
  - Add unified loadData function in admin.tsx to reduce code duplication
  - Add change-password.ts API endpoint for admin password management
  - Add logs.ts API endpoint for viewing error logs in admin panel
  - Add logErrorToFile function in logger.ts for persistent error logging
  - Add comprehensive error logging in schedule.ts (parsing, fetch, timeout, network errors)
  - Add comprehensive project structure documentation in README.md
  - Add architecture and code organization section in README.md
  - Add database information section in README.md
  - Add SQLite and bcrypt to tech stack documentation
  - Add better-sqlite3 and bcrypt dependencies to package.json
  - Add .gitignore rules for error.log and database files (data/, *.db, *.db-shm, *.db-wal)

refactor:
  - Refactor admin.tsx: extract reusable components (toggle, select, dialog footer)
  - Refactor API routes to use withAuth wrapper for consistent authentication
  - Refactor API routes to use validation utilities instead of inline validation
  - Refactor groups.ts and groups.json: move to old/data/ directory (deprecated, now using SQLite)
  - Refactor settings-loader.ts: migrate from JSON to SQLite database
  - Refactor groups-loader.ts: migrate from JSON to SQLite database
  - Refactor database.ts: improve backward compatibility for settings migration
  - Refactor admin.tsx: unify data loading functions (loadGroupsList, loadSettingsList)
  - Refactor index.tsx: add showAddGroupButton prop and conditional rendering
  - Refactor API routes: consistent error handling and method validation
  - Refactor README.md: update tech stack, project structure, and admin panel documentation
  - Refactor auth.ts: improve session management and cookie handling
  - Refactor schedule.ts: improve error handling with detailed logging and error types
  - Refactor logger.ts: add file-based error logging functionality
  - Refactor loading-context.tsx: improve error message clarity

remove:
  - Remove hello.ts test API endpoint
  - Remove groups.ts and groups.json (moved to old/data/, replaced by SQLite)

update:
  - Update .gitignore to exclude old data files, database files, and error logs
  - Update package.json: add better-sqlite3, bcrypt and their type definitions
  - Update README.md with new features, architecture, and database information
  - Update all API routes to use new wrapper system
  - Update admin panel with new settings and improved UI
  - Update sitemap.xml with cache usage comment

src/app/parser/schedule.ts

@@ -275,10 +275,101 @@ const parseLesson = (row: Element): Lesson | null => {
       const isFreeTimeReplacement = lesson.isChange && 
         (cellText.includes('Свободное время') && cellText.includes('Замена') && cellText.includes('на:'))
       
+      // Проверяем, является ли это заменой предмета на предмет
+      const isSubjectReplacement = lesson.isChange && 
+        !isFreeTimeReplacement && 
+        cellText.includes('Замена') && 
+        cellText.includes('на:')
+      
       if (isFreeTimeReplacement) {
         // Для замены "свободное время" на пару нужно парсить данные после "на:"
         // Структура: "Замена Свободное время на:</a><br> название <br> преподаватель <font> адрес <br> кабинет </font>
         
+        // Используем HTML парсинг для извлечения данных после "на:"
+        const afterOnIndex = cellHTML.indexOf('на:')
+        if (afterOnIndex !== -1) {
+          const afterOn = cellHTML.substring(afterOnIndex + 3) // +3 для "на:"
+          
+          // Пропускаем первый <br> (он идет сразу после "на:")
+          const firstBrIndex = afterOn.indexOf('<br')
+          if (firstBrIndex !== -1) {
+            // Находим конец первого <br> тега
+            const firstBrEnd = afterOn.indexOf('>', firstBrIndex) + 1
+            const afterFirstBr = afterOn.substring(firstBrEnd)
+            
+            // Извлекаем название предмета (текст до следующего <br>)
+            const secondBrIndex = afterFirstBr.indexOf('<br')
+            if (secondBrIndex !== -1) {
+              const subjectHTML = afterFirstBr.substring(0, secondBrIndex)
+              lesson.subject = subjectHTML.replace(/<[^>]+>/g, '').trim()
+              
+              // Извлекаем преподавателя (текст между вторым <br> и <font> или следующим <br>)
+              const secondBrEnd = afterFirstBr.indexOf('>', secondBrIndex) + 1
+              const afterSecondBr = afterFirstBr.substring(secondBrEnd)
+              
+              const fontIndex = afterSecondBr.indexOf('<font')
+              if (fontIndex !== -1) {
+                const teacherHTML = afterSecondBr.substring(0, fontIndex)
+                lesson.teacher = teacherHTML.replace(/<[^>]+>/g, '').trim()
+              } else {
+                // Если нет <font>, преподаватель может быть до следующего <br> или до конца
+                const thirdBrIndex = afterSecondBr.indexOf('<br')
+                if (thirdBrIndex !== -1) {
+                  const teacherHTML = afterSecondBr.substring(0, thirdBrIndex)
+                  lesson.teacher = teacherHTML.replace(/<[^>]+>/g, '').trim()
+                } else {
+                  lesson.teacher = afterSecondBr.replace(/<[^>]+>/g, '').trim()
+                }
+              }
+            } else {
+              // Если нет второго <br>, название предмета может быть до <font> или до конца
+              const fontIndex = afterFirstBr.indexOf('<font')
+              if (fontIndex !== -1) {
+                const subjectHTML = afterFirstBr.substring(0, fontIndex)
+                lesson.subject = subjectHTML.replace(/<[^>]+>/g, '').trim()
+              } else {
+                lesson.subject = afterFirstBr.replace(/<[^>]+>/g, '').trim()
+              }
+            }
+          }
+          
+          // Ищем адрес и кабинет внутри <font>
+          const fontMatch = afterOn.match(/<font[^>]*>([\s\S]*?)<\/font>/i)
+          if (fontMatch) {
+            const fontContent = fontMatch[1]
+            // Ищем паттерн: <br> адрес <br> Кабинет: номер
+            // Сначала убираем все теги и разбиваем по <br>
+            const cleanContent = fontContent.replace(/<[^>]+>/g, '|').split('|').filter(p => p.trim())
+            // Ищем адрес (первая непустая часть) и кабинет (часть с "Кабинет:")
+            for (let i = 0; i < cleanContent.length; i++) {
+              const part = cleanContent[i].trim()
+              if (part && !part.includes('Кабинет:')) {
+                const nextPart = cleanContent[i + 1]?.trim() || ''
+                const classroomMatch = nextPart.match(/Кабинет:\s*([^\s]+)/i)
+                if (classroomMatch) {
+                  lesson.place = {
+                    address: part,
+                    classroom: classroomMatch[1]
+                  }
+                  break
+                }
+              }
+            }
+          } else {
+            // Если нет <font>, ищем адрес и кабинет напрямую в тексте после "на:"
+            const addressMatch = afterOn.match(/([^<]+?)(?:<br[^>]*>|\s+)Кабинет:\s*([^<\s]+)/i)
+            if (addressMatch) {
+              lesson.place = {
+                address: addressMatch[1].replace(/<[^>]+>/g, '').trim(),
+                classroom: addressMatch[2].trim()
+              }
+            }
+          }
+        }
+      } else if (isSubjectReplacement) {
+        // Для замены предмета на предмет нужно парсить данные после "на:"
+        // Структура: "Замена [старый предмет] на:</a><br> [новый предмет] <br> [преподаватель] <font> [адрес] <br> Кабинет: [номер] </font>
+        
         // Используем HTML парсинг для извлечения данных после "на:"
         const afterOnIndex = cellHTML.indexOf('на:')
         if (afterOnIndex !== -1) {