[HIGH] Reduce widespread `any` type usage (176 occurrences across 55 files)

[NateIsern]

Description

The codebase has 176 occurrences of any type across 55 files, undermining TypeScript's primary value of catching bugs at compile time.

Affected Files (highest counts)

• packages/frontend/components/Feed/Feed.tsx — 12 occurrences
• packages/frontend/components/Feed/PostItem.tsx — 8 occurrences
• packages/frontend/services/feedService.ts — multiple
• packages/frontend/services/socketService.ts — multiple
• packages/backend/src/controllers/posts.controller.ts — multiple
• packages/backend/src/controllers/feed.controller.ts — multiple
• packages/backend/server.ts:637 — (global as any).io = io

Examples

// Backend - unsafe global
(global as any).io = io;

// Backend - untyped maps
const profilesMap = new Map<string, any>();

// Backend - unsafe casts
return await (feedController as any).transformPostsWithProfiles(...);

// Frontend - untyped event handlers
catch (error: any) { ... }

// Frontend - untyped API responses
const results: any = { posts: [] };

Expected Behavior

1. Create proper TypeScript interfaces in packages/shared-types/ for:
   • API response types
   • Socket event payloads
   • Profile/User/Post shapes
2. Replace Map<string, any> with properly typed Maps
3. Add proper type augmentation for global.io instead of as any
4. Use unknown instead of any for error catches and narrow appropriately
5. Prioritize high-traffic files first (Feed.tsx, PostItem.tsx, feedService.ts)

Impact

• Severity: High (long-term maintainability)
• Risk: Bugs slip through compilation, harder to refactor, less IDE assistance