refactor: migrate from better-sqlite3 to Prisma (#170)

* refactor: migrate from better-sqlite3 to Prisma

- Install Prisma dependencies and initialize with SQLite
- Create Prisma schema matching existing database structure
- Replace database.js with Prisma-based database service
- Update all API routes, tRPC routers, and WebSocket handler
- Convert TypeScript types to match Prisma schema
- Update build process to include Prisma migrations
- Remove better-sqlite3 dependency

All database operations now use Prisma while maintaining SQLite backend.

* fix: flatten server data in installed scripts API responses

- Transform Prisma nested server objects to flattened fields expected by frontend
- Update getAllInstalledScripts, getInstalledScriptsByServer, and getInstalledScriptById
- Server names should now display correctly in the installed scripts table
- Use nullish coalescing operators for better null handling

* fix: ensure DATABASE_URL is set in .env for Prisma during updates

- Add ensure_database_url() function to update.sh
- Function checks if .env exists and creates from .env.example if needed
- Automatically adds DATABASE_URL if not present
- Call function after restore_backup_files() in update flow
- Fixes Prisma client generation error during updates

prisma/schema.prisma

@@ -0,0 +1,45 @@
+generator client {
+  provider = "prisma-client-js"
+}
+
+datasource db {
+  provider = "sqlite"
+  url      = env("DATABASE_URL")
+}
+
+model InstalledScript {
+  id                Int       @id @default(autoincrement())
+  script_name       String
+  script_path       String
+  container_id      String?
+  server_id         Int?
+  execution_mode    String
+  installation_date DateTime? @default(now())
+  status            String
+  output_log        String?
+  web_ui_ip         String?
+  web_ui_port       Int?
+  server            Server?   @relation(fields: [server_id], references: [id], onDelete: SetNull)
+  
+  @@map("installed_scripts")
+}
+
+model Server {
+  id                 Int                @id @default(autoincrement())
+  name               String             @unique
+  ip                 String
+  user               String
+  password           String?
+  auth_type          String?            @default("password")
+  ssh_key            String?
+  ssh_key_passphrase String?
+  ssh_port           Int?               @default(22)
+  color              String?
+  created_at         DateTime?          @default(now())
+  updated_at         DateTime?          @updatedAt
+  ssh_key_path       String?
+  key_generated      Boolean?           @default(false)
+  installed_scripts  InstalledScript[]
+  
+  @@map("servers")
+}