Phase 2: Migrate core infrastructure (DB, session, server, API) to TypeScript

[jessefreeman]

Scope:
Convert foundational backend CoffeeScript modules to TypeScript: database layer, session management, main server bootstrap, and API layer.

Priority Order:

1. server/db/*.coffee
2. server/session/*.coffee
3. server/server.coffee & server/webapp.coffee
4. server/api.coffee

Key Actions per file:

• Copy existing compiled .js → .ts
• Introduce interfaces/types for data models and records
• Replace var with const/let, remove CoffeeScript IIFE/binding patterns
• Add explicit return types and error handling
• Remove .coffee version after verification

Acceptance Criteria:

• All targeted core files exist as .ts with no TypeScript errors
• Unit / smoke tests pass for startup & one sample API call
• CoffeeScript originals removed for migrated subset

Deliverables:

• Type definitions for DB records & session objects
• Updated build script using tsc (no coffee step) for these modules

Risks:

• Implicit dynamic structures → mitigate with incremental typing (any → interfaces)
• Circular dependencies revealed by ES module resolution

[jessefreeman]

Parent epic: #6