refactor(uload): remove unused schema tables, keep only clicks

The uload-server reads links from sync_changes (local-first via mana-sync)
and never used the Drizzle schema tables (users, accounts, workspaces, links).
Strip uload-database package to only the clicks table which is needed for
performant analytics aggregation with proper SQL indexes.

- Remove 5 unused tables (users, accounts, workspaces, links, relations)
- Keep only uload.clicks with indexes on link_id, clicked_at, country, device_type
- Simplify uload-database package from ~190 LOC to ~40 LOC

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -691,7 +691,7 @@ Each service owns a PostgreSQL schema within the shared database:
 | `todo` | todo server | tasks, projects, reminders |
 | `traces` | traces server | locations, cities, POIs, guides |
 | `presi` | presi server | decks, slides, themes, shares |
-| `uload` | uload server | users, links, clicks |
+| `uload` | uload server | clicks only (links via sync_changes) |
 | `cards` | cards package | decks, cards, study progress |
 
 ### Using pgSchema