AsciiArt startup banner: drop the 1s sleep, fix the once-only race, rotate banners

Problem

com.dotcms.util.AsciiArt prints a single hardcoded startup banner and blocks the startup thread for a full second doing it:

private static boolean artDone = false;   // not thread-safe
...
if (artDone) return;                       // check-then-set race
...
Thread.sleep(1000);                        // 1s added to every boot

Three things worth fixing:

1. Thread.sleep(1000) — a full second of dead time on every startup, purely so the banner lingers. Nothing reads it that fast; the log keeps it.
2. artDone is a plain boolean with a check-then-set — two threads racing doArt() can both print.
3. One banner, hardcoded. A small rotating set is nicer and costs nothing.

Proposal

• Replace the single banner with a String[] of banners, pick one per boot.
• AtomicBoolean.compareAndSet for the once-only guard.
• Drop the Thread.sleep(1000).

Notes

Java text blocks still process escape sequences, so any ASCII art containing \ must escape it as \\ or the file will not compile (error: illegal escape character). Use \s to preserve a trailing space, since text blocks strip incidental trailing whitespace.

Acceptance criteria

• Startup banner still prints exactly once
• No Thread.sleep in the startup path
• dotcms-core compiles

Start at com.dotcms.util.AsciiArt and inspect the doArt() entry point, including the current banner text, guard, and sleep. Replace the single-banner behavior as proposed, preserve valid Java text-block escaping, and compile dotcms-core to verify that the startup banner prints exactly once without Thread.sleep.