Decks tab: a deck list page, with the builder on its own screen

The deck list is no longer a sidebar pinned beside the builder; on every
screen size the Decks tab opens to a deck list page (DeckList), and picking
a deck opens its builder full-width with an "All decks" back button. The
list shows each deck as an art tile (or a compact row, toggleable) with its
colors, size against its format, owned %, cost and legality, and can be
searched, filtered by format and sorted (recently opened, name, format,
size, cost, owned %). Rename/duplicate/export/delete live in each deck's
menu and beside the builder's title; New deck now asks for a format too,
defaulting to the last one used.

A deck's cover art is the commander, else its priciest nonland, unless a
card is chosen with "Use as cover" in the card preview. The cover is stored
in decks.cover_oracle_id (migration 0007) and synced as DeckDoc.cover; a
document carrying one is version 3, so the sync server must be updated
before clients publish covers. The list's stats come from one
all_deck_contents query, summarised with the builder's own analysis code,
now in deckAnalysis.ts.

Closes #9
Closes #11
Closes #12

crates/mtgc-core/src/model.rs

@@ -269,6 +269,9 @@ pub struct Deck {
     /// The commander card's oracle id (meaningful for Commander/Brawl formats).
     pub commander_oracle_id: Option<String>,
     pub notes: String,
+    /// The card whose art headlines the deck in the deck list, if chosen;
+    /// `None` leaves the pick to the UI.
+    pub cover_oracle_id: Option<String>,
 }
 
 /// Aggregate stats about the owned library, for a dashboard-style summary.