Implements Issue #106: Read Gist APIs with two new endpoints for retrieving
encrypted gists and their metadata.

## New Features

### GET /api/gists/[id] - Gist Metadata Endpoint
- Returns public gist metadata excluding sensitive fields (PIN hash/salt)
- Implements proper cache headers (5min for regular, no-cache for one-time)
- Type-safe response using Omit utility type

### GET /api/blobs/[id] - Encrypted Blob Endpoint
- Returns encrypted blob data as binary with security headers
- Implements proper cache headers (1hr for regular, no-cache for one-time)
- Sets Content-Disposition for secure file downloads

## Key Implementation Details

- **Error Handling**: Uses ErrorCode enums instead of string matching for reliability
- **One-Time View**: Automatically deletes gists after successful retrieval
- **Expiry Check**: Returns 410 Gone for expired gists based on expires_at
- **Security**: Excludes edit_pin_hash, edit_pin_salt, encrypted_metadata from responses
- **Edge Runtime**: Compatible with Cloudflare Workers global performance
- **Logger Integration**: Proper error tracking with context-specific loggers

## Testing

- 23 comprehensive tests with 100% coverage for both endpoints
- Tests error scenarios: 400, 404, 410, 500 status codes
- Tests one-time view deletion and cache headers
- Tests large blob handling and empty blob edge cases

## API Error Improvements

- Added ApiErrors.gone() method for 410 status responses
- Enhanced error response consistency across endpoints
- Added GetGistMetadataResponse type for type-safe responses

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <claude@ghostpaste.dev>

Replaces all console.error calls with proper logger usage for consistency
and better error tracking across the API layer.

## Changes

- **api-errors.ts**: Replace console.error with createLogger("api-errors")
- **gists/route.ts**: Replace console.error with createLogger("api:gists:post")
- **api-errors.test.ts**: Update test mocks to use logger instead of console.error

## Benefits

- Consistent logging format with timestamps and context
- Better error tracking and debugging capability
- Follows established logging patterns throughout codebase
- Proper error object handling instead of raw console output

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <claude@ghostpaste.dev>