Add tag filtering to invoiceTags list utility

[Kingsman-99]

Description

src/lib/invoiceTags.ts manages tags on invoices but provides no utility to filter a list of invoices by one or more tags. Callers implement this filter ad-hoc in multiple places, leading to inconsistent behaviour when an invoice has multiple tags.

Acceptance Criteria

• filterByTags(invoices: Invoice[], tags: string[], opts?: { matchAll?: boolean }): Invoice[] exported from src/lib/invoiceTags.ts
• Default (matchAll: false): returns invoices that have any of the given tags
• matchAll: true: returns only invoices that have all of the given tags
• Empty tags array returns all invoices unchanged
• Exported from the existing barrel export if one exists
• Unit tests: any-match, all-match, empty tags returns all, no matches returns empty array

Context

• Target file: src/lib/invoiceTags.ts
• Invoice type from src/lib/types — use existing import pattern in the file