Fix bulk card image downloader to use Scryfall CDN

[phughk]

Card image downloader: CDN cache + real rate limiting

Summary

Image downloads went through Scryfall's rate-limited API one card at a time.
A single 429 froze all downloads for a flat 5 minutes.
This adds a local cache of Scryfall's CDN image URLs, built via bulk data or per-set search, so most downloads skip the API and hit the unthrottled CDN directly.
Rate limiting itself is also fixed: correct per-endpoint pacing, and honoring Retry-After instead of a blanket cooldown.

Key changes

• CdnUuidCache — local per-set cache: card/lang/face → CDN image UUID. Read-only on the gameplay path; a miss queues a background sync instead of blocking.
• ScryfallBulkDataSync — one-shot download of Scryfall's full catalog (~350MB) to populate the cache for every set at once.
• ScryfallSetSync — per-set fallback via /cards/search, for when only a few sets are missing.
• ScryfallRateLimiter — replaces the old ad-hoc pacing/cooldown code; matches Scryfall's real per-endpoint limits and respects Retry-After.
• ImageFetcher, GuiDownloadFilteredCardImages, GuiDownloadService — prefer CDN URLs when cached, warm the cache before a bulk run, wait out cooldowns instead of skipping.
• DialogDownloadCardImages (desktop) / CardImageBrowserScreen (mobile) — new "sync bulk data" and "clear CDN cache" buttons.
• FView, Forge, SplashScreen — first-run prompt offering the bulk sync.
• New tests (CdnUuidCacheTest, ScryfallSetSyncTest), new gson dependency, new translation strings.

Component interaction

flowchart LR
    subgraph UI
        Dialog[DialogDownloadCardImages /<br/>CardImageBrowserScreen]
    end

    subgraph "Gameplay image path"
        IF[ImageFetcher<br/>Swing/LibGDX impls]
    end

    subgraph "Bulk download path"
        GDF[GuiDownloadFilteredCardImages]
        GDS[GuiDownloadService]
    end

    subgraph "Sync sources"
        SetSync[ScryfallSetSync<br/>per-set /cards/search]
        BulkSync[ScryfallBulkDataSync<br/>full catalog file]
    end

    Cache[(CdnUuidCache<br/>per-set .json.gz)]
    RL{{ScryfallRateLimiter}}

    Dialog -->|Download button| GDF
    Dialog -->|Sync Bulk Data button| BulkSync
    Dialog -->|Clear CDN Cache button| Cache

    IF -->|getCdnUrlIfCached — read-only| Cache
    GDF -->|isSetCached / getCdnUrlIfCached| Cache
    GDF -->|warm missing sets| SetSync
    GDF --> GDS

    Cache -->|miss: queue background sync| SetSync
    SetSync -->|mergeSetEntriesWithFaces| Cache
    BulkSync -->|mergeSetEntriesWithFaces| Cache

    SetSync -.->|acquire / 429| RL
    BulkSync -.->|acquire — listing call only| RL
    GDS -.->|acquire / 429 / cooldown wait| RL
    IF -.->|acquire / 429 / shouldSkip| RL

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Bulk sync sequence

sequenceDiagram
    participant User
    participant Dialog as DialogDownloadCardImages
    participant Bulk as ScryfallBulkDataSync
    participant RL as ScryfallRateLimiter
    participant API as api.scryfall.com
    participant Files as *.scryfall.io (bulk file host)
    participant Cache as CdnUuidCache

    User->>Dialog: Click "Sync Bulk Data"
    Dialog->>User: Confirm ~350MB download?
    User-->>Dialog: Confirm
    Dialog->>Bulk: sync(progressListener, cancelled)

    Bulk->>RL: acquire()
    Bulk->>API: GET /bulk-data
    API-->>Bulk: listing JSON
    Bulk->>Bulk: find "default_cards" download_uri

    Bulk->>Files: GET default_cards file (gzip, unthrottled)
    loop stream + parse each JSONL line
        Files-->>Bulk: next card record
        Bulk->>Bulk: group by set → cn → lang → [front, back]
        Bulk-->>Dialog: onProgress(bytes/%, cards seen)
        Dialog-->>User: update progress bar
    end

    loop for each set collected
        Bulk->>Cache: mergeSetEntriesWithFaces(setCode, entries)
        Cache->>Cache: write {set}.json.gz, drop stale in-memory entry
    end

    Bulk-->>Dialog: return setCount
    Dialog->>Dialog: re-enable buttons, refresh total/downloaded/missing stats
    Dialog-->>User: "N sets synced"

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Reviewer notes

• Bulk sync is ~350MB — confirm the size is prominent in the prompt.
• Cooldowns now block-and-wait instead of skip — confirm cancel actually interrupts the wait.
• Leftover debug System.out.printlns in Forge.java / SplashScreen.java.
• First-run prompt fires from three places (FView, Forge.afterDbLoaded, SplashScreen) — check for double-prompting.
• gson version pinned explicitly in forge-gui/pom.xml — check for conflicts elsewhere in the build.
• Sync/clear-cache UI logic is duplicated between desktop and mobile, not shared.

[github-actions]

This PR has not been updated in a while nad has been marked on stale. Stale PRs will be auto closed

[phughk]

Will tackle tonight or tomorrow night

[phughk]

For context

• the other prs are closed (forge-extras mirror, cli tool)
• local only cdn uuid resolution
• resolution comes from api instead of bulk exports
• cdn resolution is non-blocking
• pr message has been re-written to cover details

[phughk]

Closing in favour of #11709