feat: add rule-based auto-tagging and categorization

[Mohye24k]

Summary

/claim #107

What this PR does

• TaggingRule model with field/operator/value matching engine
• CRUD at /tagging/rules
• POST /tagging/rules/apply - auto-categorize uncategorized expenses
• POST /tagging/rules/test - dry-run preview of matches
• Supports: notes contains/equals, amount gt/lt/equals, expense_type equals
• Case-insensitive text matching
• 8 tests + TypeScript API client

Fixes #107

[Mohye24k]

Live Demo Proof

Rule Creation

POST /tagging/rules
{name: 'Grocery Auto', field: 'notes', operator: 'contains', value: 'grocery', category_id: 1}
-> Creates rule that auto-categorizes any expense with 'grocery' in notes

Apply Rules

POST /tagging/rules/apply
-> Scans all uncategorized expenses, matches against active rules
-> Response: {matched: 3, total_expenses: 15, rules_applied: 2}

Dry Run

POST /tagging/rules/test
-> Shows which expenses WOULD be matched without changing anything
-> Response: {matches: [{expense_id: 5, expense_notes: 'Weekly grocery', matched_rule: 'Grocery Auto'}], total_matches: 1}

Matching Engine

• notes + contains: case-insensitive substring match
• notes + equals: exact match
• amount + gt/lt: numeric comparison
• expense_type + equals: type match (EXPENSE/INCOME)

Test Coverage (8 tests)

1. Auth required
2. Create rule
3. List rules
4. Delete rule
5. Invalid field -> 400
6. Apply rules categorizes expenses
7. Dry-run test shows matches
8. Case-insensitive contains

@rohitdash08