refactor: clean up codebase, remove dead code and obsolete docs

Remove influencer-era documentation, unused components, boilerplate
assets, and ghost tiktok cron job. Add supplier invoice management,
document API routes, and PWA icons. Replace boilerplate README.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/helpers.ts

@@ -136,6 +136,7 @@ export function makeTransaction(overrides: Partial<Transaction> = {}): Transacti
     category: 'uncategorized',
     is_business: null,
     invoice_id: null,
+    supplier_invoice_id: null,
     potential_invoice_id: null,
     journal_entry_id: null,
     mcc_code: null,
@@ -235,6 +236,8 @@ export function makeDocumentAttachment(
     digitization_date: '2024-06-15T14:30:00Z',
     journal_entry_id: null,
     journal_entry_line_id: null,
+    prev_version_hash: null,
+    last_integrity_check_at: null,
     created_at: '2024-06-15T14:30:00Z',
     updated_at: '2024-06-15T14:30:00Z',
     ...overrides,