[#8] Add Dart language support

[LahaLuhem]

Adds Dart to the languages the plugin scores (alongside Java, Kotlin, Python).

Scope

• Hints on methods, top-level functions, getters/setters, factory constructors,
  and named constructors with non-trivial bodies. Default generative
  constructors and body-less named constructors are intentionally excluded.
• Class-level hint only when the class has at least one scorable member.
• Dart 3 supported: switch expressions, destructuring patterns, || patterns,
  when guards, sealed/base/final/interface modifiers, records.
• Null safety: ?? scores like an OR sequence; ??=, !, ?. score 0.
• async / async* / sync* / await / yield add no points themselves —
  only the structural code inside them does.

Tests

Ported the Java/Python fixtures (LogicalOperations, ExceptionStatements,
LoopStatements, Recursion, ExamplesFromArticle) plus Dart-specific
fixtures (NullSafety, PatternMatching, SwitchExpressions,
AsyncGenerators). All pass via ./gradlew test.

Build

• New bundledPlugin("Dart", "253.28294.51") dependency.

Manual verification in ./gradlew runIde confirmed hints render correctly
and the "High code complexity" inspection picks up Dart methods.

Note: also bumps IntelliJ Platform Gradle Plugin 2.10.5→2.11.0 and Gradle
wrapper 8.5→8.14.3 (required to depend on the Dart plugin)

[LahaLuhem]

@nikolaikopernik Not sure about the Gradle plugin bumps. I chose to start building on top of cleaner versions