feat(typescript): add core infrastructure modules

- Add centralized API type definitions (types/api.d.ts)
  - Interfaces for all API responses matching Go handler JSON
  - Snake_case field names matching actual API responses
  - Source file references in comments for verification

- Add API client module (api.ts)
  - Procedural get/post/put/delete functions
  - Automatic auth header injection
  - Exported to window for cross-module access

- Add DOM utilities (dom.ts)
  - escapeHtml for safe HTML rendering
  - querySelector wrappers with null checks
  - Element creation helpers

- Add event delegation helpers (events.ts)
  - Reusable event delegation pattern
  - Data attribute selectors for dynamic content

- Add localStorage wrapper (storage.ts)
  - Type-safe token management
  - Theme persistence helpers

web/src/events.ts

@@ -0,0 +1,117 @@
+function onDelegatedClick(selector: string, handler: (element: HTMLElement, event: MouseEvent) => void): void {
+    document.addEventListener('click', (event: MouseEvent) => {
+        const target = event.target as HTMLElement;
+        const element = target.closest(selector) as HTMLElement | null;
+        if (element) {
+            handler(element, event);
+        }
+    });
+}
+
+function onDelegatedSubmit(selector: string, handler: (form: HTMLFormElement, event: Event) => void): void {
+    document.addEventListener('submit', (event: Event) => {
+        const target = event.target as HTMLElement;
+        const form = target.closest(selector) as HTMLFormElement | null;
+        if (form) {
+            handler(form, event);
+        }
+    });
+}
+
+function onDelegatedChange(selector: string, handler: (element: HTMLElement, event: Event) => void): void {
+    document.addEventListener('change', (event: Event) => {
+        const target = event.target as HTMLElement;
+        const element = target.closest(selector) as HTMLElement | null;
+        if (element) {
+            handler(element, event);
+        }
+    });
+}
+
+function onDelegatedKeydown(selector: string, handler: (element: HTMLElement, event: KeyboardEvent) => void): void {
+    document.addEventListener('keydown', (event: KeyboardEvent) => {
+        const target = event.target as HTMLElement;
+        const element = target.closest(selector) as HTMLElement | null;
+        if (element) {
+            handler(element, event);
+        }
+    });
+}
+
+function getDataAttribute(element: HTMLElement, name: string): string | undefined {
+    return element.dataset[name];
+}
+
+function setDataAttribute(element: HTMLElement, name: string, value: string): void {
+    element.dataset[name] = value;
+}
+
+function onClick(element: HTMLElement | null, handler: (event: MouseEvent) => void): void {
+    if (element) {
+        element.addEventListener('click', handler);
+    }
+}
+
+function onSubmit(element: HTMLFormElement | null, handler: (event: Event) => void): void {
+    if (element) {
+        element.addEventListener('submit', handler);
+    }
+}
+
+function onChange(element: HTMLElement | null, handler: (event: Event) => void): void {
+    if (element) {
+        element.addEventListener('change', handler);
+    }
+}
+
+function onKeydown(element: HTMLElement | null, handler: (event: KeyboardEvent) => void): void {
+    if (element) {
+        element.addEventListener('keydown', handler);
+    }
+}
+
+function onInput(element: HTMLElement | null, handler: (event: Event) => void): void {
+    if (element) {
+        element.addEventListener('input', handler);
+    }
+}
+
+function preventDefault(event: Event): void {
+    event.preventDefault();
+}
+
+function stopPropagation(event: Event): void {
+    event.stopPropagation();
+}
+
+(window as any).events = {
+    onDelegatedClick,
+    onDelegatedSubmit,
+    onDelegatedChange,
+    onDelegatedKeydown,
+    getDataAttribute,
+    setDataAttribute,
+    onClick,
+    onSubmit,
+    onChange,
+    onKeydown,
+    onInput,
+    preventDefault,
+    stopPropagation
+};
+
+export {
+    onDelegatedClick,
+    onDelegatedSubmit,
+    onDelegatedChange,
+    onDelegatedKeydown,
+    getDataAttribute,
+    setDataAttribute,
+    onClick,
+    onSubmit,
+    onChange,
+    onKeydown,
+    onInput,
+    preventDefault,
+    stopPropagation
+};