feat(amm): source liquidity tokens app-side + add custom tokens by id

Move the liquidity token selector off the module's stateful newPositionContext
onto a lean, app-owned surface, and let users add unlisted tokens by id.

FFI: new stateless `resolve_tokens` op — the app passes an explicit id set and
gets uniform selector rows `{ definitionId (base58), name, totalSupply, holdingId,
balance }`, held tokens first, unresolvable/non-fungible ids omitted. Reuses the
per-token definition/holding logic from `context`, without the network/status
envelope. Unit-tested.

Module: `resolveTokens(request, wallet_open)` reads the definitions + wallet and
calls the op (ids wrapped in a map — the universal-module glue only marshals
map/scalar inputs, not bare lists).

Backend: the app owns the id set — configured tokens (TOKENS_CONFIG) plus the
user's persisted custom ids. Held-but-unlisted tokens are NOT auto-listed (the
list mirrors the swap side); a token you hold still shows its balance once listed.
`addCustomToken` validates a pasted id by resolving its on-chain definition, then
persists it to CUSTOM_TOKEN_CONFIG (defaulting to the per-user app-data store, with
a HOME fallback so persistence never silently no-ops on an empty path).

QML: NewPositionForm/LiquidityPage take tokens/walletReady/loadingTokens as inputs
and drive selection + custom-token resolution through the backend; dropped all
newPositionContext reads and the selectable/status/code row fields.

Tests: custom-token.mjs creates token D on-chain (left out of the token config)
and verifies pasting its id resolves, selects, and persists it across a reload.
The setup script mints token D and initializes/prints the isolated
CUSTOM_TOKEN_CONFIG store

modules/amm/ffi/src/api/mod.rs

@@ -21,7 +21,7 @@ pub use request::{
     AddLiquidityPlanRequest, AddLiquidityQuoteRequest, ConfigIdRequest, ContextRequest,
     CreatePoolPlanRequest, CreatePoolQuoteRequest, FeeTiersRequest, PairIdsRequest, PoolIdRequest,
     ProgramIdRequest, RemoveLiquidityPlanRequest, RemoveLiquidityQuoteRequest, ResolvePoolRequest,
-    SwapExactInPlanRequest, SwapExactInQuoteRequest, SwapExactOutPlanRequest,
+    ResolveTokensRequest, SwapExactInPlanRequest, SwapExactInQuoteRequest, SwapExactOutPlanRequest,
     SwapExactOutQuoteRequest, SwapPairRequest, SyncReservesPlanRequest, TokenHoldingsRequest,
     TokenIdsRequest,
 };
@@ -83,6 +83,11 @@ pub fn context(request: ContextRequest) -> AmmResult {
     context::context(request).map_err(Into::into)
 }
 
+/// Resolves an app-provided set of token ids into selector rows (lean successor to `context`).
+pub fn resolve_tokens(request: ResolveTokensRequest) -> AmmResult {
+    context::resolve_tokens(request).map_err(Into::into)
+}
+
 /// Derives the canonical account ids for a swap pair (tokens in either order).
 pub fn swap_pair(request: SwapPairRequest) -> AmmResult {
     swap::swap_pair(request).map_err(Into::into)