LINUS ROUND 1: Delete dead code (rust/c), generic Store[T], tests, slim main.go

- Removed rust-service/, c-runtime/, kafka stubs
- Generic Store[T] pattern with real tests
- Slimmed main.go from 324 to ~50 lines
- Added config, middleware, store, ledger, pdf tests
- Frontend SPA shell with router
- Binary: 15.5MB -> 12MB

web/assets/modules/support.js

@@ -0,0 +1,10 @@
+// Support module
+export async function render(container) {
+  container.innerHTML = `
+    <header class="module-header">
+      <h1>Support</h1>
+      <p class="subtitle">Ärenden och kundtjänst</p>
+    </header>
+    <p>Modulen laddas...</p>
+  `;
+}