feat: Smart error handling with CREATE TABLE detection

[keyamasabaya]

Session Management

• Fix dropRestart() race condition: add session_write_close() to force
  disk write before redirect (fixes import not restarting from line 0)
• Add new action restartFromBeginning() to restart import without DROP
• Register restart_import route in Application.php and Request.php

CREATE TABLE Detection

• Add FileAnalysisService::hasCreateTableFor() method
  • Scans first 10MB of SQL file for CREATE TABLE statements
  • Supports both regular and gzipped files
  • Case-insensitive pattern matching with backtick support

Smart Error UI

• Enrich SSE error response with hasCreateTable boolean
• Conditional error buttons based on context:
  • "Table already exists" + CREATE TABLE found → "Drop & Restart"
  • "Table already exists" + no CREATE TABLE → help message
  • "Table doesn't exist" + CREATE TABLE found → "Restart from Beginning"
  • "Table doesn't exist" + no CREATE TABLE → help message
• Rename "Start Over (resume)" → "Resume" for clarity

Files Modified

• src/Controllers/BigDumpController.php (dropRestart fix + new action)
• src/Services/FileAnalysisService.php (hasCreateTableFor method)
• src/Services/AjaxService.php (smart error UI logic)
• src/Core/Application.php (restart_import route)
• src/Core/Request.php (restart_import validation)

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