fix: dedup fund_capture alerts for same-date sibling records and add clear-all

fund_capture alerts for a symbol with multiple capture records sharing one
as_of re-fired every batch cycle: the single comparison-state slot
ping-ponged between sibling evidence URLs, and the pre-check dedup key
never matched the stored buildDedupKey format. Track a seen-set of URLs in
comparison state and align dedup-key construction with buildDedupKey.
Also add alerts.clearAll (hard delete) with an immediate-refresh bell.

app/server/src/trpc/router.ts

@@ -2085,6 +2085,14 @@ const alertsRouter = router({
       return { ok: true };
     }),
 
+  /** Permanently delete all alert events for the current user. */
+  clearAll: protectedProcedure
+    .mutation(async ({ ctx }) => {
+      const userId = ctx.userId as string;
+      ctx.db.prepare('DELETE FROM alert_events WHERE user_id = ?').run(userId);
+      return { ok: true };
+    }),
+
   /** Get unacknowledged alert count. */
   unackedCount: protectedProcedure
     .query(async ({ ctx }) => {