feat: await initial database connection (#10869)

# Which Problems Are Solved

When Postgres was not ready when the API was started, the API failed
immediately.
This made task orchestration hard, especially in a platform agnostic
way:

- The current health check in the Nx target `@zitadel/api:prod` uses the
timeout command, which is not installed on all platforms and behaves
unpredictably
- The current health check in the Nx target `@zitadel/api:prod` requires
the DB to have been started using `@zitadel/zitadel:db`

# How the Problems Are Solved

- Additional configuration option `Database.Postgres.AwaitInitialConn`
is added and defaults to *0m* for backwards compatibility.
- If a duration is configured, the API retries to ping the database
until it succeeds
- The API sleeps for a second between each ping.
- It emits an info-level log with the error on each try.
- When the configured duration times out before the ping is successful,
the error is returned and the command exits with a failure code.
- When the ping succeeds within the configured duration, the API goes on
with the init, setup or start phase.

# Additional Context

- Relates to internally reported problems with the current DB health
check command
[here](https://zitadel.slack.com/archives/C07EUL5H83A/p1759915009839269?thread_ts=1759912259.410789&cid=C07EUL5H83A)
and
[here](https://zitadel.slack.com/archives/C07EUL5H83A/p1759918324246249?thread_ts=1759912259.410789&cid=C07EUL5H83A).

(cherry picked from commit 7ba6870baf)

internal/database/postgres/pg.go

@@ -29,15 +29,16 @@ const (
 )
 
 type Config struct {
-	Host            string
-	Port            int32
-	Database        string
-	MaxOpenConns    uint32
-	MaxIdleConns    uint32
-	MaxConnLifetime time.Duration
-	MaxConnIdleTime time.Duration
-	User            User
-	Admin           AdminUser
+	Host             string
+	Port             int32
+	Database         string
+	AwaitInitialConn time.Duration
+	MaxOpenConns     uint32
+	MaxIdleConns     uint32
+	MaxConnLifetime  time.Duration
+	MaxConnIdleTime  time.Duration
+	User             User
+	Admin            AdminUser
 	// Additional options to be appended as options=<Options>
 	// The value will be taken as is. Multiple options are space separated.
 	Options string
@@ -127,8 +128,18 @@ func (c *Config) Connect(useAdmin bool) (*sql.DB, *pgxpool.Pool, error) {
 	if err != nil {
 		return nil, nil, err
 	}
-
-	if err := pool.Ping(context.Background()); err != nil {
+	if err = pool.Ping(context.Background()); err != nil && c.AwaitInitialConn > 0 {
+		waitUntil := time.Now().Add(c.AwaitInitialConn)
+		for time.Now().Before(waitUntil) {
+			logging.Infof("retrying initial database connection in a second: %v", err)
+			time.Sleep(time.Second)
+			if err = pool.Ping(context.Background()); err == nil {
+				break
+			}
+		}
+	}
+	if err != nil {
+		pool.Close()
 		return nil, nil, err
 	}