fix(core): resolve new market equity metadata on save/import (#697)

[AtomicTrxn]

Description

Summary

• fix new market-equity save/import preparation so MIC and quote currency are enriched before persistence validation
• reuse the same live symbol enrichment path for manual save, bulk save, and import apply
• keep validation strict for genuinely unresolved symbols and preserve manual quote-mode behavior

Root cause

activities_service validated new market equities before live symbol enrichment in manual save and import-apply flows. That meant ticker-only equities like DPZ or HD could pass import check but still fail on save/apply because exchange_mic and quote_ccy were not yet populated.

Fix

• enrich missing MIC via live symbol resolution before validation for eligible market equities
• resolve quote currency using explicit input -> existing asset -> provider quote -> MIC fallback -> terminal currency before validation
• return the existing market-data lookup error when a new market equity still cannot be resolved

Tests

• cargo test -p wealthfolio-core activities_service
• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo test --workspace

Fixes #697

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