Rework library sync around a JSON document; add card filters

Sync

The previous design put the merge inside SQL: timestamp-stamping triggers,
a tombstone table, per-device SQLite snapshots, a device id in the database,
and row merges written as correlated-subquery UPDATEs. All of that schema
was inherited by desktop, and the merge was very hard to verify.

Replace it with a single JSON document plus a three-way merge in plain Rust.
Storing the last-read remote document as the merge base makes "who changed
what" and "what was deleted" derivable, which removes the tombstone table,
the updated_at columns and all eight triggers. It also makes a single shared
file safe: if a publish is lost the remote is unchanged, so the next merge
re-detects the local edits and republishes rather than reading their absence
as a deletion. That removes the need for per-device files and for device
identity entirely. Schema impact drops to one column, decks.uuid.

Conflicts resolve to "theirs", which is required for convergence rather than
chosen for taste — preferring ours has each device re-asserting its own value
forever. Every such choice is reported to the user.

SQLite becomes invisible: the working copy lives in the app data dir and the
user only ever names a .json file. There is always a document, defaulting to
private storage, so edits are never stranded with nowhere to be saved.
Pointing at a file that doesn't exist yet moves the current library there;
pointing at one that does adopts it. A converter brings a pre-document
library.db across.

Android reaches the folder through the Storage Access Framework rather than
MANAGE_EXTERNAL_STORAGE, so no storage permission is declared at all.

Filters

Track card origin in reference.db: Universes Beyond, digital-only and
Un-set cards, plus numeric power/toughness. Each origin flag is derived as
"every printing", not "any printing" — ordinary cards get reprinted into
those sets, and Lightning Bolt appearing in Marvel Commander must not hide
it. Non-numeric power ("*", "1+*") stays NULL so it drops out of range
filters instead of being compared as zero.

Also wire up filters over data already present: price range, format legality
(restricted counts as legal) and "can be a commander". All of these degrade
silently against an older reference.db rather than failing every query.

The shared criteria live in one component used by both filter panels, as a
compact row of icon toggles.

Card Search gains the Library tab's bulk selection: checkboxes in both views,
select-all, and a bulk add-to-deck with a single undo for the whole batch.

crates/mtgc-core/src/sql/library/0005_deck_uuid.sql

@@ -0,0 +1,21 @@
+-- v5 — a stable, device-independent identity for decks.
+--
+-- Sync merges two copies of the library by matching entities across them.
+-- `library_cards` and `deck_cards` already have global keys (`oracle_id`, and
+-- `(deck, oracle_id)`), but `decks.id` is per-device autoincrement: two devices
+-- both hand out id 3 to different decks. Matching on `name` instead would work
+-- until someone renames a deck, at which point the merge sees a delete plus an
+-- unrelated create and the deck's contents are stranded.
+--
+-- This is the *only* schema sync needs. Change tracking is not stored here:
+-- the merge derives what changed (and what was deleted) by comparing against
+-- the last-synced document, so there are no timestamp columns, no tombstones,
+-- and no triggers.
+
+ALTER TABLE decks ADD COLUMN uuid TEXT;
+
+-- Existing decks predate the column. `randomblob` is SQLite's own CSPRNG, so
+-- this needs no help from Rust and no new dependency.
+UPDATE decks SET uuid = lower(hex(randomblob(16))) WHERE uuid IS NULL;
+
+CREATE UNIQUE INDEX idx_decks_uuid ON decks(uuid);

crates/mtgc-core/src/sql/reference_schema.sql

@@ -24,7 +24,27 @@ CREATE TABLE IF NOT EXISTS oracle_cards (
     -- absent (falls back to `printings`).
     image_uri           TEXT NOT NULL DEFAULT '',
     back_image_uri      TEXT NOT NULL DEFAULT '',
-    default_scryfall_id TEXT NOT NULL DEFAULT ''
+    default_scryfall_id TEXT NOT NULL DEFAULT '',
+    -- Boolean: this card exists *only* as Universes Beyond (Lord of the Rings,
+    -- Warhammer 40,000, Marvel, ...). Derived after the printings pass from
+    -- `printings.universes_beyond`, deliberately as "every printing is UB"
+    -- rather than "some printing is UB" — ordinary cards get reprinted into UB
+    -- sets (Lightning Bolt is in Marvel Commander) and must not be caught by
+    -- a filter meant to exclude other IPs' characters.
+    universes_beyond    INTEGER NOT NULL DEFAULT 0,
+    -- Boolean: exists only on Arena/MTGO (Alchemy rebalances and the like), so
+    -- it can never be part of a physical collection. Same every-printing
+    -- rollup as `universes_beyond`.
+    digital_only        INTEGER NOT NULL DEFAULT 0,
+    -- Boolean: exists only in "funny" sets — Unglued, Unhinged, Unstable,
+    -- Unfinity. Not legal in any normal format.
+    funny               INTEGER NOT NULL DEFAULT 0,
+    -- Printed power/toughness, NULL when the card isn't a creature *or* when
+    -- the value isn't a plain number ("*", "1+*", "X"). NULL therefore means
+    -- "can't be compared numerically", and such cards drop out of a
+    -- power/toughness range filter rather than being coerced to 0.
+    power               REAL,
+    toughness           REAL
 );
 CREATE INDEX IF NOT EXISTS idx_oracle_name_lower ON oracle_cards(name_lower);
 CREATE INDEX IF NOT EXISTS idx_oracle_ci ON oracle_cards(color_identity);
@@ -62,7 +82,13 @@ CREATE TABLE IF NOT EXISTS printings (
     rarity           TEXT NOT NULL DEFAULT '',
     image_uri        TEXT NOT NULL DEFAULT '',
     back_image_uri   TEXT NOT NULL DEFAULT '',  -- transform/MDFC/reversible back face
-    price_usd        REAL NOT NULL DEFAULT 0    -- Scryfall "prices.usd", 0 if unknown
+    price_usd        REAL NOT NULL DEFAULT 0,   -- Scryfall "prices.usd", 0 if unknown
+    -- Boolean: Scryfall lists "universesbeyond" in this printing's promo_types.
+    universes_beyond INTEGER NOT NULL DEFAULT 0,
+    -- Boolean: this printing isn't available on paper (Scryfall `games`).
+    digital          INTEGER NOT NULL DEFAULT 0,
+    -- Boolean: this printing comes from a "funny" set (Scryfall `set_type`).
+    funny            INTEGER NOT NULL DEFAULT 0
 );
 CREATE INDEX IF NOT EXISTS idx_printings_oid ON printings(oracle_id);