fix: resolve SonarQube findings and Next.js Image warnings

SonarQube/SonarLint fixes:
- Remove unused imports (useMemo, PROVIDER_ENDPOINTS, updateSettings, APP_CONFIG)
- Add PropTypes validation to all components receiving props
- Fix accessibility issues (semantic buttons, ARIA attributes, form labels)
- Replace array index keys with stable identifiers
- Extract duplicate getStatusDisplay function in providers page
- Fix negated conditions for better readability
- Add node: prefix to Node.js imports in localDb.js
- Fix optional chaining in pricing lookup
- Add explanatory comments to empty catch blocks
- Consolidate duplicate OAuth flow branches
- Change parseInt to Number.parseInt
- Disable false positive rules in VS Code settings

Next.js Image fixes:
- Add style={{ width: "auto", height: "auto" }} to all Image components
- Resolves aspect ratio warnings without triggering lint issues

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/landing/components/Navigation.js

@@ -10,12 +10,17 @@ export default function Navigation() {
     <nav className="fixed top-0 z-50 w-full bg-[#181411]/80 backdrop-blur-md border-b border-[#3a2f27]">
       <div className="max-w-7xl mx-auto px-6 h-16 flex items-center justify-between">
         {/* Logo */}
-        <div className="flex items-center gap-3 cursor-pointer" onClick={() => router.push("/")}>
+        <button
+          type="button"
+          className="flex items-center gap-3 cursor-pointer bg-transparent border-none p-0"
+          onClick={() => router.push("/")}
+          aria-label="Navigate to home"
+        >
           <div className="size-8 rounded bg-linear-to-br from-[#f97815] to-orange-700 flex items-center justify-center text-white">
             <span className="material-symbols-outlined text-[20px]">hub</span>
           </div>
           <h2 className="text-white text-xl font-bold tracking-tight">9Router</h2>
-        </div>
+        </button>
 
         {/* Desktop menu */}
         <div className="hidden md:flex items-center gap-8">