fix: return total count from paginated list APIs for accurate pagination

[octo-patch]

Fixes #2338

Problem

The paginated list endpoints for channels, users, tokens, redemptions, and logs returned only the current page's data without a total record count. The berry-theme frontend inferred the total heuristically:

count={items.length + (items.length % ITEMS_PER_PAGE === 0 ? 1 : 0)}

This means that after loading the first page (e.g. 10 items), MUI TablePagination received count = 11, showing only 2 navigable pages at a time. Users had to click "Next" repeatedly to reach later pages — they could never jump directly to page 5 or the last page.

Solution

Backend — Add Count* functions in the model layer that execute a SELECT COUNT(*) with the same filter conditions as the corresponding Get* functions:

• model.CountChannels()
• model.CountUsers()
• model.CountUserTokens(userId)
• model.CountRedemptions()
• model.CountAllLogs(...) (respects all filter params)
• model.CountUserLogs(...) (respects all filter params)

Each GetAll* controller now runs the count query and includes a total field in the JSON response. This change is backward-compatible — old clients and other themes simply ignore the new field.

Frontend (berry theme) — Each paginated list view:

1. Stores total from the API response in a dedicated state variable (channelCount, userCount, etc.)
2. Passes it directly to TablePagination's count prop, making all pages visible immediately
3. Updates onPaginationChange to fetch any not-yet-loaded page when the user navigates directly (e.g. jumps from page 1 to page 8)
4. Updates search handlers to set count = data.length for search results (which are returned all at once)

Testing

• Load the channel list with > 10 channels: pagination now shows the correct total pages immediately
• Navigate directly to a page beyond what was initially loaded: the page data is fetched on demand
• Perform a keyword search: pagination reflects the number of search results
• Non-berry themes and existing API consumers are unaffected (they ignore the new total field)