Fix boot sequence alignment, rate limiter memory leak, and docs gaps

- base.js: Fix boot sequence title centering — old formula was off by 1
  char for odd-length app names (PULSE, GANDALF). Remove unused `bar`
  variable. New logic computes left/right padding independently to
  handle both even and odd title lengths correctly.
- node/middleware.js: Prune expired rate-limit entries from Map when
  size exceeds 5000 to prevent unbounded memory growth. Also use
  req.socket?.remoteAddress as fallback for req.ip.
- README.md: Document lt.beep() in the JS API section. Clarify Quick
  Start to distinguish core files from platform-specific helpers.
  Note that tableNav.init() and sortTable.init() require explicit calls.
- aesthetic_diff.md: Correct §8 toast icon format — base.js uses
  bracketed symbols [✓][✗][!][i], not >> prefix as previously stated.

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

base.js

@@ -297,12 +297,14 @@
     overlay.style.display = 'flex';
     overlay.style.opacity = '1';
 
-    const name    = (appName || 'TERMINAL').toUpperCase();
-    const bar     = '═'.repeat(Math.max(0, 41 - name.length));
-    const pad     = ' '.repeat(Math.max(0, Math.floor((39 - name.length) / 2)));
+    const name      = (appName || 'TERMINAL').toUpperCase();
+    const titleStr  = name + ' v1.0';
+    const innerWidth = 43;
+    const leftPad   = Math.max(0, Math.floor((innerWidth - titleStr.length) / 2));
+    const rightPad  = Math.max(0, innerWidth - titleStr.length - leftPad);
     const messages = [
       '╔═══════════════════════════════════════════╗',
-      '║' + pad + name + ' v1.0' + pad + '║',
+      '║' + ' '.repeat(leftPad) + titleStr + ' '.repeat(rightPad) + '║',
       '║           BOOTING SYSTEM...              ║',
       '╚═══════════════════════════════════════════╝',
       '',