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/components/mindmap/nodes/BaseNode.tsx

@@ -20,7 +20,13 @@ interface BaseNodeProps extends NodeProps {
   borderStyle?: "solid" | "dashed" | "dotted";
 }
 
-export function BaseNode({ data, selected, icon, color, borderStyle = "solid" }: BaseNodeProps) {
+export function BaseNode({
+  data,
+  selected,
+  icon,
+  color,
+  borderStyle = "solid",
+}: BaseNodeProps): React.JSX.Element {
   return (
     <div
       className={`

apps/web/src/components/mindmap/nodes/ConceptNode.tsx

@@ -4,7 +4,7 @@ import type { NodeProps } from "@xyflow/react";
 import type { BaseNodeData } from "./BaseNode";
 import { BaseNode } from "./BaseNode";
 
-export function ConceptNode(props: NodeProps) {
+export function ConceptNode(props: NodeProps): React.JSX.Element {
   return (
     <BaseNode
       {...props}

apps/web/src/components/mindmap/nodes/IdeaNode.tsx

@@ -4,7 +4,7 @@ import type { NodeProps } from "@xyflow/react";
 import type { BaseNodeData } from "./BaseNode";
 import { BaseNode } from "./BaseNode";
 
-export function IdeaNode(props: NodeProps) {
+export function IdeaNode(props: NodeProps): React.JSX.Element {
   return (
     <BaseNode
       {...props}

apps/web/src/components/mindmap/nodes/ProjectNode.tsx

@@ -4,7 +4,7 @@ import type { NodeProps } from "@xyflow/react";
 import type { BaseNodeData } from "./BaseNode";
 import { BaseNode } from "./BaseNode";
 
-export function ProjectNode(props: NodeProps) {
+export function ProjectNode(props: NodeProps): React.JSX.Element {
   return (
     <BaseNode
       {...props}

apps/web/src/components/mindmap/nodes/TaskNode.tsx

@@ -4,7 +4,7 @@ import type { NodeProps } from "@xyflow/react";
 import type { BaseNodeData } from "./BaseNode";
 import { BaseNode } from "./BaseNode";
 
-export function TaskNode(props: NodeProps) {
+export function TaskNode(props: NodeProps): React.JSX.Element {
   return (
     <BaseNode
       {...props}