fix(a12): decode real blockchain-config param values

[Gift-Stack]

config.get read the real config dictionary but emitted value: "0" for every labeled fee param (18 storage, 20/21 gas, 24/25 fwd, 34 validators) — so A12 showed 0 for exactly the params that matter, and A9's storage-fee story had no real prices behind it.

What this does

Decodes labeled params for real using @ton/ton's own TL-B parsers — no hand-rolling:

• p18 configParse18 (storage prices), p20/p21 configParseGasLimitsPrices, p24/p25 configParseMsgPrices, p34 parseValidatorSet.
• New decodeConfigParam(id, cell) → { label, value }[]; wrapped in try/catch so an unexpected tag falls back to the raw boc (never fabricated data). Raw boc is preserved for labeled params too. The raw-param path is unchanged.

Contract type (kept in lockstep)

Added DecodedConfigField + a named ConfigParam interface to rpc/contract.ts (value unchanged; new optional fields?). Updated bridge handler, mock-bridge (same shape, non-zero fixtures), and ConfigPanel (renders decoded fields, Kind badge now uses param.kind, filter/copy cover decoded values).

Verification

• pnpm tsc green; bridge smoke ALL OK.
• Live-bridge check printed real sandbox values, e.g. p20 gas_price=655360000, gas_limit=1000000; p24 lump_price=10000000, bit_price=655360000; p18 cell_price_ps=135, mc_cell_price_ps=500000.