feat(csv): add CsvImport pure parser with tests

Introduces CsvImport.extractNumbers() which scans comma/tab/semicolon/
pipe-delimited text, normalises each cell via PhoneNorm.digitsOnly, and
returns deduplicated phone numbers (9-13 digits) in original order.
Adds 6 JVM unit tests covering dash formatting, multi-column CSV,
tab/semicolon delimiters, Korean country-code stripping, deduplication,
and short/non-phone token rejection. Total unit tests: 41.

Constraint: CsvImport has no Android dependencies — must remain a pure JVM object.
Confidence: high
Scope-risk: local
Reversibility: trivial
Directive: UI integration follows in next commit.
Tested: 6 CsvImportTest cases pass (./gradlew testDebugUnitTest)
Not-tested: streaming large files, BOM handling, Windows CRLF edge cases
Related: v1.12 / vc13

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