API endpoint and UI to list/audit all attachments across a project or Org

### Problem Statement

## Problem

Organizations uploading attachments to Sentry currently have no way to get a centralized view of all attachments being uploaded across their projects.

### Current Limitations

1. **No bulk API endpoint** - The only attachment API requires a specific `event_id`:
GET /api/0/projects/{org}/{project}/events/{event_id}/attachments/

There's no way to list all attachments for a project or organization without first knowing which events have attachments.

2. **No UI dashboard** - Attachments can only be viewed on individual issue detail pages. There's no "Attachments" overview or audit page.

3. **On the overview page, there should be source attribution** - When attachments appear, users should be able to easily trace which SDK, service, or code path generated them.

### Use Cases

- **Debugging unexpected uploads**: A user reported uploading "a lot of attachments" but cannot identify their source across multiple services
- **Cost management**: Attachments count toward data quotas; teams need visibility to optimize usage
- **Compliance/auditing**: Organizations need to audit what data is being sent to third-party services
- **Operational visibility**: DevOps teams need to monitor attachment streams for anomalies

### User Feedback

> "We are uploading a lot of attachments to Sentry but it's not obvious what their source is. I am currently assessing our services to see if I can uncover who/what/where these are coming from, but I am hoping that Sentry has some way of inspecting the uploaded attachments stream? It would be very helpful to be able to see _what_ is uploaded to Sentry, in Sentry.

### Solution Brainstorm

## Proposed Solutions

### Option 1: New API Endpoint
Add a project-level attachments listing endpoint:

GET /api/0/projects/{org}/{project}/attachments/

With support for:
- Pagination
- Date range filtering
- Filtering by attachment type/name
- Returns: attachment metadata, associated event_id, issue, timestamp, size

### Option 2: UI Dashboard
Add an "Attachments" section in Project Settings or a dedicated page showing:
- Recent attachment uploads (table view)
- Aggregate stats (count, total size, by type)
- Filtering/search capabilities
- Links to associated events/issues

### Option 3: Enhanced Metadata
Store and expose additional metadata with attachments:
- SDK name/version that uploaded it
- Release/environment context
- Custom tags for source identification

### Product Area

APIs

Start by reviewing the existing event-scoped attachments endpoint, GET /api/0/projects/{org}/{project}/events/{event_id}/attachments/, and compare it with the proposed project-level endpoint. Done requires a decided scope for the API, dashboard, filtering, pagination, and source metadata rather than the current set of brainstormed options.

Written by the indexing model from the issue text.