DB migrations: bundled SQL applied automatically after install

Each PROSERVE ZIP can now ship a _migrations/ subfolder with versioned SQL
scripts. The launcher applies them right after extraction, in the same
install session as the binary copy, so the user never lands on a PROSERVE
build whose schema doesn't match its code.

Service (PSLauncher.Core/Migrations)
- IDatabaseMigrationService + DatabaseMigrationService (MySqlConnector,
  BSD-licensed). Each .sql runs in a transaction; on failure the DB
  state is rolled back and the install completes (files only) but the
  user is warned to fix the connection / replay later.
- Tracking table _launcher_migrations (filename, applied_at, checksum,
  duration_ms) — same model as Flyway / Doctrine. Already-applied scripts
  are skipped on subsequent installs. Modified scripts trigger a warning
  log without blocking.
- Custom SQL splitter that respects strings/comments/backticks so a single
  .sql file can contain multiple statements separated by `;`.
- DatabasePasswordProtector: DPAPI CurrentUser scope for the MySQL password
  in config.json (same protection as the license key).

Config (PSLauncher.Models/LocalConfig.cs)
- New DatabaseConfig section: Host=localhost, Port=3306, User=root, empty
  password, Database=proserve, AutoApplyMigrations=true. Defaults match a
  fresh XAMPP install. Override via Settings (next commit).

Install pipeline (MainViewModel)
- After ZipInstaller.InstallAsync and before declaring the install complete,
  if AutoApplyMigrations and a _migrations/ folder exists, run
  ApplyMigrationsAsync with progress reporting (per-file %, filename in
  footer). Failure shows MsgMigrationFailed dialog explaining XAMPP must
  be running and pointing to Settings → Database for connection params.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/PSLauncher.Core/PSLauncher.Core.csproj

@@ -12,6 +12,8 @@
     <PackageReference Include="Polly" Version="8.4.2" />
     <PackageReference Include="NSec.Cryptography" Version="24.4.0" />
     <PackageReference Include="System.Security.Cryptography.ProtectedData" Version="8.0.0" />
+    <!-- MySQL client : MySqlConnector (BSD-3-Clause), pas Oracle MySql.Data (GPL) -->
+    <PackageReference Include="MySqlConnector" Version="2.3.7" />
   </ItemGroup>
 
   <ItemGroup>