Add comprehensive thesis management system with database migration

This commit introduces a complete thesis management interface and migrates
the system from YAML-based storage to SQLite:

Core Changes:
- Add Database.php helper class with PDO connection and entity management
- Add list.php for viewing all theses with filtering and sorting
- Add edit.php for modifying existing thesis records
- Add import.php for migrating legacy YAML data to SQLite
- Add justfile with development tasks (serve, init-test-db, etc.)

Documentation:
- Add MIGRATION.md with complete migration guide and architecture docs
- Update README.md with database setup and Just recipe instructions
- Update .gitignore to exclude test databases and error logs

Modified Forms:
- Enhanced formulaire.php with transaction-based SQLite processing
- Updated index.php with database-driven form options
- Improved thanks.php to read from database views

The new architecture provides:
- Normalized database schema (19 tables, 2 views)
- Transaction safety and referential integrity
- CRUD operations for thesis management
- Filtering by year, orientation, AP program, publication status
- Secure file handling with metadata tracking

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

front-backend/test_db.php

@@ -0,0 +1,40 @@
+<?php
+// Simple test script to verify database connection and queries
+require_once 'Database.php';
+
+try {
+    $db = Database::getInstance();
+    echo "✓ Database connection successful\n";
+
+    // Test counting theses
+    $count = $db->countPublishedTheses();
+    echo "✓ Found {$count} published theses\n";
+
+    // Test getting theses
+    $theses = $db->getPublishedTheses(5, 0);
+    echo "✓ Retrieved " . count($theses) . " theses\n";
+
+    if (count($theses) > 0) {
+        $first = $theses[0];
+        echo "\nFirst thesis:\n";
+        echo "  ID: " . $first['id'] . "\n";
+        echo "  Title: " . $first['title'] . "\n";
+        echo "  Author(s): " . ($first['authors'] ?? 'N/A') . "\n";
+        echo "  Year: " . $first['year'] . "\n";
+
+        // Test getting single thesis
+        $thesis = $db->getThesisById($first['id']);
+        if ($thesis) {
+            echo "✓ Successfully retrieved thesis details\n";
+            echo "  Orientation: " . ($thesis['orientation'] ?? 'N/A') . "\n";
+            echo "  AP Program: " . ($thesis['ap_program'] ?? 'N/A') . "\n";
+            echo "  Files: " . (count($thesis['files'] ?? [])) . "\n";
+        }
+    }
+
+    echo "\n✓ All tests passed!\n";
+
+} catch (Exception $e) {
+    echo "✗ Error: " . $e->getMessage() . "\n";
+    exit(1);
+}