feat: suggest subscriptions from a bank statement

[AmrMsCLL]

Stacked on #49. This is 11g of as2026-10-05-strata-phase-11-next-batch-2.md.

What changes

• Recurring gains Import a statement. You pick a CSV export from a bank or card, and it is read in the browser. The file is never uploaded, and the server is unchanged.
• The parser handles quoted cells, comma, semicolon or tab delimiters, day-first, month-first or year-first dates, and both decimal styles (1.234,56 and 1,234.56). Columns are found by name in several languages, or by what they hold, and can be changed by hand.
• Only money going out counts. Charges are grouped by a cleaned description, with card noise, references and numbers removed. A group is suggested when it repeats weekly, monthly, quarterly or yearly with amounts within 25%: at least three charges, or two for yearly.
• Known services from the catalogue fill in the name, category and cancel link. A suggestion already tracked in the chosen space is shown but can't be selected.
• The chosen suggestions are added through the existing POST /spaces/:id/subscriptions, starting from the last charge's date.

Verification

• Frontend: test/statement.spec.tsx (4 passed: parsing, dates, amounts, columns and suggestions) and test/subscriptions.spec.tsx (5 passed, including the import flow).
• Lint and build pass.
• Not checked against real exports from specific banks.