feat: add collaborative interview scheduling

Add candidate decisions, co-interviewer accounts, scheduled interview inbox and calendar views, candidate-safe meeting links, shared documents, and private live notes backed by RabbitMQ.

Extend the disposable integration environment to validate PostgreSQL migrations, seeded users, interview lifecycle behavior, and RabbitMQ fanout.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

backend/internal/security/security.go

@@ -1,6 +1,7 @@
 package security
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"time"
@@ -18,6 +19,22 @@ type Claims struct {
 	jwt.RegisteredClaims
 }
 
+type claimsContextKey struct{}
+
+func WithClaims(ctx context.Context, claims Claims) context.Context {
+	return context.WithValue(ctx, claimsContextKey{}, claims)
+}
+
+func ClaimsFromContext(ctx context.Context) (Claims, bool) {
+	claims, ok := ctx.Value(claimsContextKey{}).(Claims)
+	return claims, ok
+}
+
+func UserIDFromContext(ctx context.Context) (uint, bool) {
+	claims, ok := ClaimsFromContext(ctx)
+	return claims.UserID, ok && claims.UserID != 0
+}
+
 type ITokenManager interface {
 	Issue(uint, string, string) (string, error)
 	Parse(string) (Claims, error)