Add small in-memory cache for archive/league/match pages

[adrunkhuman]

Problem

Repeated back/forward navigation refetches and reparses pages that were already loaded.

Goal

Add a small, bounded in-memory cache so repeated navigation is instant for recently visited pages.

Scope

• Cache parsed domain objects in site/service layer.
• Keys:
  • archive/seasons: SeasonID (fallback canonical URL)
  • league pages: LeagueKey
  • match pages: MatchID
• Keep r as explicit refresh that bypasses/updates cache.

Suggested limits (initial)

• archives: 2-4
• leagues: 8-16
• matches: 32-64

Non-goals

• No persistence on disk.
• No broad caching framework.

Acceptance criteria

• Reopening recent season/league/match does not hit network.
• Cache remains bounded.
• Existing parsing behavior and tests stay unchanged.