[EPAC-1988]: reduce LobbyistService parser complexity

[riddim-developer-bot]

Why

LobbyistService.swift had three cyclomatic complexity violations in ZIP parsing, CSV row parsing, and communication mapping. This PR decomposes those branches without changing the public LobbyistService API.

What changed

• Split ZIP local-header parsing into private helpers for header reads, entry matching, and stored/deflated payload decoding.
• Reworked the RFC 4180 CSV parser around a small private parser state and private character-processing helpers.
• Extracted communication matching, subject formatting, and date sorting helpers.
• Added LobbyistServiceTests covering quoted fields, embedded commas, embedded newlines, escaped quotes, empty fields, CRLF rows, and skip-header behavior.

Trade-offs not taken

• Did not replace the parser with a third-party library, per issue scope.
• Kept the test access as a DEBUG-only internal hook while the extracted implementation helpers remain private.

Test plan

• swiftlint lint --strict --only-rule cyclomatic_complexity ios/epac/Util/LobbyistService.swift — passed, 0 violations.
• swiftlint --strict ios/epacTests/LobbyistServiceTests.swift — passed, 0 violations.
• cd ios && make build — passed; Xcode emitted existing Swift macro redundant Sendable warnings.
• python3 scripts/localization/check_localizations.py --github-warnings — exited 0; reported existing missing onboarding.welcome.title localization warnings.
• cd ios && make test — built and ran, but failed on existing snapshot baseline mismatches; new LobbyistServiceTests executed, with one CRLF assertion exposing a parser edge case that this PR then fixed.
• xcodebuild test ... -skip-testing:epacTests/SnapshotTests -skip-testing:epacUITests — new LobbyistServiceTests passed; command still failed on existing unrelated FollowPreferenceAdapterTests.savedMemberNameReflectsPostalCodeStore state leakage.

Reviewer-Boundary: review-only

Resolves EPAC-1988