feat(token): add name/symbol/decimals metadata to initialization

[unixfundz]

Closes #310

Changes

contracts/token/src/storage.rs

• Added Name, Symbol, Decimals variants to InstanceKey enum
• Added name(), set_name(), symbol(), set_symbol(), decimals(), set_decimals() accessors (instance storage — persisted)

contracts/token/src/lib.rs

• Extended initialize() to accept name: String, symbol: String, decimals: u32
• Added name(), symbol(), decimals() public query methods

contracts/token/src/test.rs

• Updated setup() helper to pass metadata values ("CosmosVote Token", "CVT", 7)
• Added test_metadata_name, test_metadata_symbol, test_metadata_decimals, test_metadata_custom_values

Notes

• Metadata is stored in instance storage (same tier as admin/supply) — persisted and cheaply accessible
• decimals defaults to 7 (Stellar standard) if somehow absent