Add Sentry integration sink

[willibrandon]

Description:
Create Sentry sink for automatic error tracking and monitoring. Sentry is widely used in the Go ecosystem for production error monitoring.

Package: github.com/willibrandon/mtlog/adapters/sentry

Proposed API:

import mtlogsentry "github.com/willibrandon/mtlog/adapters/sentry"

logger := mtlog.New(
    mtlog.WithConsole(),
    mtlogsentry.WithSentry(
        "https://xxx@sentry.io/project",
        mtlogsentry.WithEnvironment("production"),
        mtlogsentry.WithRelease("v1.2.3"),
        mtlogsentry.WithSampling(0.1),
        mtlogsentry.WithMinLevel(core.ErrorLevel), // Only send errors by default
    ),
)

// Custom fingerprinting
mtlogsentry.WithFingerprinter(func(event *core.LogEvent) []string {
    // Custom logic to group similar errors
    return []string{event.MessageTemplate.Text, event.Properties["ErrorType"]}
})

Features:

• Automatic error grouping/fingerprinting
• Stack trace capture from error values
• Breadcrumb support from lower level logs
• Rate limiting and sampling
• User context enrichment
• Transaction/span integration
• Release tracking
• Environment tagging

Breadcrumb Collection:

// Info/Debug logs become breadcrumbs
logger.Debug("Connecting to database")
logger.Info("User {UserId} authenticated", userID)
// Error includes above as breadcrumbs in Sentry
logger.Error("Failed to process payment: {Error}", err)

Integration with Context:

// Attach user context
ctx = mtlogsentry.WithUser(ctx, sentryUser{
    ID: "user-123",
    Email: "user@example.com",
})
logger.WithContext(ctx).Error("Payment failed")

Implementation Notes:

• Should batch events for efficiency
• Cache stack traces to avoid recomputation
• Only send ERROR and FATAL levels by default
• Consider memory-bounded breadcrumb buffer
• Support both DSN string and sentry.ClientOptions