feature: add "Browse Images" tab to editor's "insert image" dialog to facilitate image reuse (no upload again) 🤖

[mrjbj]

What changes I've made

• Added a third "Browse Images" tab to the rich text editor's Insert Image modal. This gives user ability to browse and re-use images previously uploaded or referenced before (e.g. logos, QR-Codes, etc.).
• New GET /images backend endpoint returning paginated, searchable images scoped to the authenticated account
• New BrowseImagesPanel frontend component with thumbnail grid, filename search, pagination, and LQIP placeholders
• Invalidates browse cache after uploading a new image so it appears immediately
• No database migration required — uses existing images table with account_id

Why I've made these changes

When inserting previously uploaded images (logos, QR codes, etc.) into the editor, users must either remember and paste the exact URL or re-upload the file. This tab lets users browse and select from all images already uploaded to their account, eliminating the need to maintain a manual list of image URLs.

How I've tested these changes

• Started dev stack, opened rich text editor fields across event settings, product forms, and email templates
• Verified three tabs appear: Paste URL, Upload Image, Browse Images
• Browse tab displays account images in a thumbnail grid with filenames
• Search filters images by filename with debounced input
• Clicking a thumbnail selects it (purple border), clicking Insert Image places it in the editor
• Uploaded a new image via Upload tab, switched to Browse — new image appeared
• Confirmed TypeScript validation passes (npx tsc --noEmit — no new errors)

Checklist

• I have read the contributing guidelines.
• My code follows the coding standards of the project.
• I have tested my changes, and they work as expected.
• I understand that this PR will be closed if I do not follow the contributor
  guidelines and if this PR template is left unedited.