docs: add weekly smoke test cases and prerequisites

[thepastaclaw]

Issue

Closes #771

Summary

Adds formalized weekly smoke test specification covering all implemented user stories from docs/user-stories.md, SPV-only on testnet.

New files:

• docs/test-cases.md — 32 test cases across all feature areas (WAL, SND, ALK, IDN, DPN, DPY, TOK, DOC, DEV, NET)
• docs/test-prerequisites.md — Environment setup, .env configuration for SPV testnet, bank wallet concept, cleanup procedures

Test case structure:

Each test case includes: Use Case ID, Test Case ID, Short Description, Pre-Conditions, Test Steps, Test Data, Expected Result, and Post-Condition.

Coverage:

• Wallet management (create, import, switch, rename, lock/unlock, remove, balances, addresses, SPV status, tx history)
• Send/receive (send tDASH, QR receive, fee estimation)
• Asset locks (create)
• Identity operations (register, top-up, view keys, refresh)
• DPNS (register username, view owned names, view contests)
• DashPay (create profile, search profiles)
• Token operations (view balances, search tokens)
• Contracts/documents (import contract, query documents)
• Developer tools (Platform info)
• Network/settings (network selection, theme, developer mode, onboarding wizard)

Notes:

• SPV-only — no RPC mode tests at this point
• Recommended execution order provided for test dependency chain
• Bank wallet pattern for fund management (per issue requirements)

Summary by CodeRabbit

• Documentation
  • Added comprehensive test case documentation covering smoke test scenarios for the Dash Evo Tool in SPV testnet mode, including test suites for Wallet Management, Send and Receive, Asset Locks, Identity Operations, DPNS, DashPay, Tokens, Contracts, Documents, Developer Tools, and Network settings.
  • Added test prerequisites and setup documentation detailing environment configuration, SPV mode enablement, test wallet funding procedures, and cleanup steps.