fix: Restore all files lost during destructive rebase

A previous `git pull --rebase origin main` dropped 177 local commits,
losing 3400+ files across admin-v2, backend, studio-v2, website,
klausur-service, and many other services. The partial restore attempt
(660295e2) only recovered some files.

This commit restores all missing files from pre-rebase ref 98933f5e
while preserving post-rebase additions (night-scheduler, night-mode UI,
NightModeWidget dashboard integration).

Restored features include:
- AI Module Sidebar (FAB), OCR Labeling, OCR Compare
- GPU Dashboard, RAG Pipeline, Magic Help
- Klausur-Korrektur (8 files), Abitur-Archiv (5+ files)
- Companion, Zeugnisse-Crawler, Screen Flow
- Full backend, studio-v2, website, klausur-service
- All compliance SDKs, agent-core, voice-service
- CI/CD configs, documentation, scripts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

edu-search-service/internal/database/database.go

@@ -0,0 +1,133 @@
+package database
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// DB holds the database connection pool
+type DB struct {
+	Pool *pgxpool.Pool
+}
+
+// Config holds database configuration
+type Config struct {
+	Host     string
+	Port     string
+	User     string
+	Password string
+	DBName   string
+	SSLMode  string
+}
+
+// NewConfig creates a new database config from environment variables
+func NewConfig() *Config {
+	return &Config{
+		Host:     getEnv("DB_HOST", "localhost"),
+		Port:     getEnv("DB_PORT", "5432"),
+		User:     getEnv("DB_USER", "postgres"),
+		Password: getEnv("DB_PASSWORD", "postgres"),
+		DBName:   getEnv("DB_NAME", "breakpilot"),
+		SSLMode:  getEnv("DB_SSLMODE", "disable"),
+	}
+}
+
+func getEnv(key, defaultValue string) string {
+	if value := os.Getenv(key); value != "" {
+		return value
+	}
+	return defaultValue
+}
+
+// ConnectionString returns the PostgreSQL connection string
+func (c *Config) ConnectionString() string {
+	return fmt.Sprintf(
+		"postgres://%s:%s@%s:%s/%s?sslmode=%s",
+		c.User, c.Password, c.Host, c.Port, c.DBName, c.SSLMode,
+	)
+}
+
+// New creates a new database connection
+func New(ctx context.Context, cfg *Config) (*DB, error) {
+	config, err := pgxpool.ParseConfig(cfg.ConnectionString())
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse database config: %w", err)
+	}
+
+	// Configure connection pool
+	config.MaxConns = 10
+	config.MinConns = 2
+	config.MaxConnLifetime = time.Hour
+	config.MaxConnIdleTime = 30 * time.Minute
+
+	pool, err := pgxpool.NewWithConfig(ctx, config)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create connection pool: %w", err)
+	}
+
+	// Test connection
+	if err := pool.Ping(ctx); err != nil {
+		pool.Close()
+		return nil, fmt.Errorf("failed to ping database: %w", err)
+	}
+
+	log.Printf("Connected to database %s on %s:%s", cfg.DBName, cfg.Host, cfg.Port)
+
+	return &DB{Pool: pool}, nil
+}
+
+// Close closes the database connection pool
+func (db *DB) Close() {
+	if db.Pool != nil {
+		db.Pool.Close()
+	}
+}
+
+// RunMigrations executes all SQL migrations
+func (db *DB) RunMigrations(ctx context.Context) error {
+	// Try multiple paths for migration file
+	migrationPaths := []string{
+		"migrations/001_university_staff.sql",
+		"../migrations/001_university_staff.sql",
+		"../../migrations/001_university_staff.sql",
+	}
+
+	var content []byte
+	var err error
+	var foundPath string
+
+	for _, path := range migrationPaths {
+		absPath, _ := filepath.Abs(path)
+		content, err = os.ReadFile(absPath)
+		if err == nil {
+			foundPath = absPath
+			break
+		}
+	}
+
+	if content == nil {
+		return fmt.Errorf("failed to read migration file from any path: %w", err)
+	}
+
+	log.Printf("Running migrations from: %s", foundPath)
+
+	// Execute migration
+	_, err = db.Pool.Exec(ctx, string(content))
+	if err != nil {
+		return fmt.Errorf("failed to execute migration: %w", err)
+	}
+
+	log.Println("Database migrations completed successfully")
+	return nil
+}
+
+// Health checks if the database is healthy
+func (db *DB) Health(ctx context.Context) error {
+	return db.Pool.Ping(ctx)
+}