fix: Resolve all ESLint errors and warnings in web package

Fixes all 542 ESLint problems in the web package to achieve 0 errors and 0 warnings.

Changes:
- Fixed 144 issues: nullish coalescing, return types, unused variables
- Fixed 118 issues: unnecessary conditions, type safety, template literals
- Fixed 79 issues: non-null assertions, unsafe assignments, empty functions
- Fixed 67 issues: explicit return types, promise handling, enum comparisons
- Fixed 45 final warnings: missing return types, optional chains
- Fixed 25 typecheck-related issues: async/await, type assertions, formatting
- Fixed JSX.Element namespace errors across 90+ files

All Quality Rails violations resolved. Lint and typecheck both pass with 0 problems.

Files modified: 118 components, tests, hooks, and utilities

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

apps/web/src/lib/auth-client.ts

@@ -17,7 +17,7 @@ export const authClient = createAuthClient({
   baseURL:
     typeof window !== "undefined"
       ? window.location.origin
-      : process.env.BETTER_AUTH_URL || "http://localhost:3042",
+      : (process.env.BETTER_AUTH_URL ?? "http://localhost:3042"),
 
   // Plugins can be added here when needed
   plugins: [],
@@ -35,11 +35,11 @@ export const { signIn, signOut, useSession, getSession } = authClient;
  * Uses direct fetch since our server accepts username (not email)
  * and the default BetterAuth client expects email.
  */
-export async function signInWithCredentials(username: string, password: string) {
+export async function signInWithCredentials(username: string, password: string): Promise<unknown> {
   const baseURL =
     typeof window !== "undefined"
       ? window.location.origin
-      : process.env.BETTER_AUTH_URL || "http://localhost:3042";
+      : (process.env.BETTER_AUTH_URL ?? "http://localhost:3042");
 
   const response = await fetch(`${baseURL}/api/auth/sign-in/credentials`, {
     method: "POST",
@@ -51,11 +51,11 @@ export async function signInWithCredentials(username: string, password: string)
   });
 
   if (!response.ok) {
-    const error = await response.json().catch(() => ({}));
-    throw new Error(error.message || "Authentication failed");
+    const error = (await response.json().catch(() => ({}))) as { message?: string };
+    throw new Error(error.message ?? "Authentication failed");
   }
 
-  const data = await response.json();
+  const data = (await response.json()) as unknown;
   return data;
 }
 
@@ -65,7 +65,7 @@ export async function signInWithCredentials(username: string, password: string)
  */
 export async function getAccessToken(): Promise<string | null> {
   const session = await getSession();
-  if (!session?.data?.user) {
+  if (!session.data?.user) {
     return null;
   }
 
@@ -83,7 +83,7 @@ export async function getAccessToken(): Promise<string | null> {
     return null;
   }
 
-  return user.accessToken || null;
+  return user.accessToken ?? null;
 }
 
 /**
@@ -91,7 +91,7 @@ export async function getAccessToken(): Promise<string | null> {
  */
 export async function isAdmin(): Promise<boolean> {
   const session = await getSession();
-  if (!session?.data?.user) {
+  if (!session.data?.user) {
     return false;
   }