webui: add ESLint and eslint-typescript

I've historically found this stuff worthwhile, so let's swallow the pill.

Fortunately, sketch was happy to oblige.

- Install ESLint, @eslint/js, and typescript-eslint packages
- Configure eslint.config.mjs with recommended TypeScript ESLint rules
- Add browser globals support for DOM and web APIs
- Integrate ESLint into npm test workflow via package.json scripts
- Update Makefile to run lint checks as part of test suite
- Fix 249+ linting issues including:
  * Remove unused imports and variables (with _ prefix convention)
  * Fix case declaration issues with eslint-disable blocks
  * Remove unnecessary escape characters
  * Address prefer-const violations
  * Handle unused function parameters appropriately
- Configure ignore patterns to exclude dist/ and node_modules/
- Set rules to allow explicit 'any' types temporarily
- Convert warnings for ts-ignore, async promise executors, and unsafe optional chaining

Results:
- ESLint now runs successfully with 0 errors and only 6 warnings
- TypeScript compilation continues to work correctly
- Linting integrated into test workflow for continuous quality enforcement
- Codebase follows consistent ESLint TypeScript recommended practices

Co-Authored-By: sketch <hello@sketch.dev>
Change-ID: sd7b538be0a28d294k
diff --git a/webui/src/web-components/sketch-timeline-message.ts b/webui/src/web-components/sketch-timeline-message.ts
index 1fb8334..695ef79 100644
--- a/webui/src/web-components/sketch-timeline-message.ts
+++ b/webui/src/web-components/sketch-timeline-message.ts
@@ -1,3 +1,4 @@
+/* eslint-disable @typescript-eslint/no-explicit-any */
 import { css, html, LitElement, render } from "lit";
 import { unsafeHTML } from "lit/directives/unsafe-html.js";
 import { customElement, property, state } from "lit/decorators.js";
@@ -1124,7 +1125,7 @@
         second: "2-digit",
         hour12: true,
       });
-    } catch (e) {
+    } catch {
       return defaultValue;
     }
   }
@@ -1136,7 +1137,7 @@
     if (num === undefined || num === null) return defaultValue;
     try {
       return num.toLocaleString();
-    } catch (e) {
+    } catch {
       return String(num);
     }
   }
@@ -1150,7 +1151,7 @@
       // Use 4 decimal places for message-level costs, 2 for totals
       const decimalPlaces = isMessageLevel ? 4 : 2;
       return `$${parseFloat(String(num)).toFixed(decimalPlaces)}`;
-    } catch (e) {
+    } catch {
       return defaultValue;
     }
   }