Fix transactions batch decoding

[stefangutica]

Reasoning

• signature & guardianSignature must be decoded from hex

Proposed Changes

• decode from hex instead of base64

How to test

• transactions batch should work properly

[github-actions]

k6 load testing comparison.
Base Commit Hash: 97c06ed
Target Commit Hash: 1d9b2f5

Metric	Base				Target				Diff
	Avg	Max	90	95	Avg	Max	90	95	Avg	Max	90	95
Tokens	38.18	708.23	49.70	51.39	50.39	539.15	79.81	205.39	+31.98% 🔴	-23.87% ✅	+60.57% 🔴	+299.65% 🔴
Mex	38.33	673.03	49.72	51.35	49.88	389.77	77.82	202.29	+30.11% 🔴	-42.09% ✅	+56.50% 🔴	+293.96% 🔴
Blocks	44.80	712.73	52.50	61.92	59.72	487.00	94.44	244.46	+33.29% 🔴	-31.67% ✅	+79.91% 🔴	+294.76% 🔴
Nodes	38.22	699.67	49.72	51.34	848.26	25135.08	97.08	100.12	+2119.25% 🔴	+3492.41% 🔴	+95.25% 🔴	+95.00% 🔴
Pool	37.99	294.19	49.67	51.40	50.36	557.37	79.67	205.57	+32.56% 🔴	+89.46% 🔴	+60.41% 🔴	+299.93% 🔴
Accounts	38.13	405.32	49.69	51.34	54.31	1154.99	86.89	209.94	+42.44% 🔴	+184.96% 🔴	+74.87% 🔴	+308.88% 🔴
Transactions	47.35	1724.87	52.32	78.14	71.80	104.98	90.20	97.93	+51.63% 🔴	-93.91% ✅	+72.41% 🔴	+25.32% 🔴
Test Run Duration	60001.85				60002.40

Legend: Avg - Average Response Time, Max - Maximum Response Time, 90 - 90th Percentile, 95 - 95th Percentile
All times are in milliseconds.