chore(dashboard): add Biome config for lint + format

Nested config ("root": false) so it coexists with packages/plugin/biome.json
in this Bun workspace monorepo. Dashboard uses 2-space indent matching its
existing code style (plugin uses 4-space).

Rules match the plugin where sensible:
  - recommended rule set
  - useConst: error, noForEach: off, noAssignInExpressions: off, noConsole: off
  - noNonNullAssertion/noExplicitAny: warn
  - noUnusedImports/noUnusedVariables: warn

Scope: packages/dashboard/src/**/*.{ts,tsx,js,jsx,css,json},
excluding .d.ts, dist/, src-tauri/target/.

Run locally:
  ./node_modules/.bun/@biomejs+cli-darwin-arm64@2.4.7/node_modules/\
  @biomejs/cli-darwin-arm64/biome check packages/dashboard/src

Author: ualtinok

packages/dashboard/biome.json

@@ -0,0 +1,55 @@
+{
+    "$schema": "https://biomejs.dev/schemas/2.4.7/schema.json",
+    "root": false,
+    "vcs": {
+        "enabled": true,
+        "clientKind": "git",
+        "useIgnoreFile": true
+    },
+    "assist": {
+        "enabled": true
+    },
+    "formatter": {
+        "enabled": true,
+        "indentStyle": "space",
+        "indentWidth": 2,
+        "lineWidth": 100
+    },
+    "linter": {
+        "enabled": true,
+        "rules": {
+            "recommended": true,
+            "complexity": {
+                "noForEach": "off"
+            },
+            "style": {
+                "noNonNullAssertion": "warn",
+                "useConst": "error"
+            },
+            "suspicious": {
+                "noExplicitAny": "warn",
+                "noAssignInExpressions": "off",
+                "noConsole": "off"
+            },
+            "correctness": {
+                "noUnusedImports": "warn",
+                "noUnusedVariables": "warn"
+            }
+        }
+    },
+    "javascript": {
+        "formatter": {
+            "quoteStyle": "double",
+            "trailingCommas": "all",
+            "semicolons": "always"
+        }
+    },
+    "files": {
+        "includes": [
+            "src/**/*.{ts,tsx,js,jsx,css,json}",
+            "!src/**/*.d.ts",
+            "!dist/**",
+            "!src-tauri/target/**"
+        ]
+    }
+}