Short IDs become the canonical identifier in URLs (/i/:short_id),
MinIO/R2 storage keys, and all API responses. Hash-based deduplication
is preserved. Includes two-phase Alembic migration (003 adds nullable
column, 004 enforces NOT NULL) with a backfill script to copy storage
objects and populate short_id for existing images.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
API responses now include file_url and thumbnail_url fields. When
S3_PUBLIC_BASE_URL is configured, these point to the CDN domain;
when unset, they fall back to the existing API proxy paths so local
dev requires no additional setup. UI updated to use response URL
fields directly instead of constructing proxy URLs client-side.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
