Saved Games search, ZIP imports, playback, and engine delivery security

Engine delivery security

Restricted the engine proxy to known Stockfish assets on its configured host. Requests cannot select another upstream host, redirects are rejected, and upstream cookies and service-worker permission headers are not passed through.
Added regression tests covering host escapes, redirects, unsupported paths, safe headers, conditional requests, and local engine delivery.

Added ZIP selection to Browse… in Import Games → Paste a game or collection, alongside PGN and Analysis JSON files.
Added drag-and-drop ZIP imports through the same PGN extraction and normal game or collection import flow. Multiple PGN files, including those in folders, are combined; unrelated archive files are ignored.
Added file-integrity checks, a 64 MiB limit for both the archive and combined uncompressed PGNs, and a maximum of 1,000 archive entries. Damaged, password-protected, ZIP64 and multi-part archives show an error instead of partially importing content.
Kept game selection and duplicate detection in the existing import workflow. Browse fills the paste area without saving games; choose Continue to proceed.

Replaced category buttons with a raised Category dropdown and a collapsible Filters section that remembers its expanded state.
Added dedicated searchable Player, Source, Date and Opening filters. Opening entries show the ECO code and opening name together. Games without opening information are classified from their moves using a bundled CC0 opening dataset, refreshed and validated during release preparation.
Added a separate Saved Games window with responsive cards and remembered size and position. Window controls use gray beveled buttons.
Made game titles clickable with an Open game tooltip, and moved the remaining card actions into a hamburger menu.
Added Clear selection across pages and a progress bar for large exports that clears after completion.
Added a Browse button to the paste/import panel for choosing a PGN or JSON file.

Added automatic playback to the main Game Moves controls and consistent speed choices on players: 0.5, 1, 2, 3 or 5 seconds per move, with 2 seconds as the default. Right-click Play to choose a speed.
Added a side-by-side move table to the larger Saved Games player, with a rounded outline around the current move and automatic scrolling. Its autoplay speed is remembered.
Added a mini player directly beneath the engine continuation in Move Analysis, with spaced move labels and an outline tracking the current move.
Moved Start critical review beneath the Move Analysis heading and hid Try the best move when the played move matches the engine recommendation.
Preserved separate saved analysis runs for Browser games.
Made Board Theme and Training Profiles pop-outs fill and adapt to their browser window.