fix: sanitize input for non-HTML consumers and fix ReDoS in cache

[mmcintosh]

Description

Add input sanitization for fields served to non-HTML consumers (JWT payloads, JSON API responses, email subjects) and fix a ReDoS vulnerability in cache pattern invalidation. This is PR 3 in the AUDIT-001 remediation series.

Strategy: Input sanitization is applied only to fields consumed outside HTML templates (where PR 1's output escaping handles XSS). This prevents double-encoding.

Changes

Auth Registration Sanitization (auth.ts)

• POST /register: sanitize username, firstName, lastName (returned in JWT and API response)
• POST /register/form: sanitize same fields
• POST /accept-invitation: sanitize username
• Skipped: email (Zod-validated), password (hashed, never sanitize)

Media API Sanitization (api-media.ts)

• PATCH /:id: sanitize alt and caption fields (returned in JSON API responses via GET /api/media/:id)

Email Template Subject (email-templates-plugin/admin-routes.ts)

• POST /templates: sanitize subject field (rendered as plain text in email clients)

ReDoS Fix (cache/services/cache.ts)

• MemoryCache.invalidatePattern() and CacheService.invalidate(): escape regex metacharacters (.+|()[]{}^$\) before glob-to-regex conversion
• Previously, patterns like (a+)+* could cause catastrophic backtracking

Testing

Build Verification

• ESM build passes
• CJS build passes
• DTS (TypeScript declarations) build passes

E2E Tests

• Full E2E suite (CI)

Technical Details

4 source files changed:

File	Change
src/routes/auth.ts	sanitizeInput() on username/firstName/lastName in 3 handlers
src/routes/api-media.ts	sanitizeInput() on alt/caption in PATCH handler
src/plugins/available/email-templates-plugin/admin-routes.ts	sanitizeInput() on subject
src/plugins/cache/services/cache.ts	Escape regex metacharacters in 2 locations

Breaking Changes

None. Registration fields with HTML characters will now be stored escaped. Media alt/caption will be stored escaped.

Checklist

• Code follows project conventions
• Type checking passes
• No console errors or warnings

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Codecov Report

✅ All modified and coverable lines are covered by tests.

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