feat: base64 uploads, reusable forms, Discord roles, and UX improvements (#66)

## Summary

This PR includes multiple feature additions and fixes to improve the library application:

### 🎨 Base64 Image Upload Support
- Fixed Fastify body limit (1MB → 10MB) to accommodate base64-encoded images
- Corrected base64 size calculation and validation logic
- Improved error handling with proper 400 status codes and helpful messages
- Removed duplicate validation that was blocking uploads
- Users can now upload cover images up to 5MB (decoded size)

### 📝 Reusable Form Components
- Created 6 form components: `GameForm`, `BookForm`, `MusicForm`, `ShowForm`, `MangaForm`, `ArtForm`
- All forms support both 'add' and 'edit' modes with pre-population
- Integrated inline editing into all detail views (edit/delete buttons)
- Enhanced admin suggestions workflow with full forms instead of basic modals
- Added scroll-to-top when clicking edit in list views for better UX

### 🖼️ Default Cover Image
- Added beautiful library reading image as default cover for all media types
- Fixed static asset serving to use correct MIME types
- Updated all 12 components (6 list views + 6 detail views) to always show images

### 🔒 Tiered Rate Limiting
- Unauthenticated users: 100 requests/minute
- Authenticated users: 500 requests/minute (5x more lenient)
- Admin users: No rate limits (complete bypass via allowList)

### 🎮 Discord Integration
- Auto-assign library member role to users in NHCarrigan Discord server
- Checks server membership on every login
- Only assigns role if user is in server and doesn't have it yet
- Graceful error handling without blocking login
- Similar pattern to badge refresh flow

### 📚 Documentation
- Added comprehensive CLAUDE.md with:
  - Project structure and tech stack
  - Development workflow and commands
  - Database schema documentation
  - Authentication flow details
  - Security features
  - Code style conventions
  - Common gotchas and solutions

## Test Plan

- [x] Base64 image uploads work for cover images up to 5MB
- [x] Helpful error messages appear for validation failures
- [x] Edit/delete buttons appear on all detail views for admin users
- [x] Inline edit forms display and save correctly
- [x] Admin suggestions workflow uses full forms for all media types
- [x] Scroll-to-top works when editing from list views
- [x] Default cover image displays when no cover is provided
- [x] Static assets serve with correct MIME types
- [x] Rate limiting works correctly for different user types
- [x] Discord role assignment works on login
- [x] All builds pass without errors
- [x] No TypeScript errors

## Related Issues

Closes #65 - Base64 image upload issue

✨ This pull request was created with help from Hikari~ 🌸

Reviewed-on: #66
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

api/src/app/services/game.service.ts

@@ -33,9 +33,6 @@ export class GameService {
     if (!validateStringLength(data.notes, MAX_LENGTHS.NOTES)) {
       throw new Error(`Notes must be ${MAX_LENGTHS.NOTES} characters or less.`);
     }
-    if (!validateStringLength(data.coverImage, MAX_LENGTHS.URL)) {
-      throw new Error(`Cover image URL must be ${MAX_LENGTHS.URL} characters or less.`);
-    }
 
     // Validate rating
     if (!validateRating(data.rating)) {
@@ -45,8 +42,14 @@ export class GameService {
     // Validate cover image URL
     if (data.coverImage) {
       if (data.coverImage.startsWith("data:")) {
-        const sizeInBytes = data.coverImage.length * 0.75;
-        if (sizeInBytes > MAX_LENGTHS.DATA_URL) {
+        // Extract just the base64 data (after the comma)
+        const base64Data = data.coverImage.split(",")[1];
+        if (!base64Data) {
+          throw new Error("Invalid image data URL format.");
+        }
+        // Calculate decoded size: base64 is ~4/3 larger than original, so multiply by 0.75
+        const decodedSizeInBytes = base64Data.length * 0.75;
+        if (decodedSizeInBytes > MAX_LENGTHS.DATA_URL) {
           throw new Error("Cover image must be under 5MB.");
         }
         if (!validateDataUrl(data.coverImage)) {