DC-004: Fix all 19 ESLint warnings (zero remaining)

Removed unused imports (path, validateStartupConfig, platformPaths),
renamed unused destructures (_timeout, _logEntry), replaced nested
ternaries with lookup tables, added eslint-disable comments on
require-await functions that are intentionally async for API stability,
and extracted helper functions to reduce max-depth and complexity in
app.js, dns.js, provider-dns.js, and site.js. All 879 tests pass.

dashcaddy-api/src/utils/logging.js

@@ -21,11 +21,8 @@ function createLogger(LOG_LEVEL) {
     
     if (Object.keys(data).length) entry.data = data;
     
-    const fn = level === 'error'
-      ? console.error
-      : level === 'warn'
-        ? console.warn
-        : console.info;
+    const logFns = { error: console.error, warn: console.warn, info: console.info, debug: console.info };
+    const fn = logFns[level] || console.info;
     fn(JSON.stringify(entry));
   }