Make live route writes cheaper so the prefix handler keeps up (closes #96)

The live route tables lose their random UUID key; the row id the
prefix-length sample draws is declared as the integer key. The prefix
tables are keyed by prefix and keep only first_seen; a batch inserts only
prefixes not stored yet. A route update sets only the columns that
change. Each kept index names the queries using it. Every write goes
through one connection kept for writing, with a 1 GiB page cache; reading
connections get 16 MiB, heap limits rise to 1.5 and 2 GiB (README
"Memory"). Batch writes go in key order. A benchmark run by hand writes
250,000 updates on 5 million routes faster than the feed's 10,000 a
second; a live run follows.

Model: opus-5-5

internal/routewatch/prefixhandler.go

@@ -12,7 +12,6 @@ import (
 	"git.eeqj.de/sneak/routewatch/internal/logger"
 	"git.eeqj.de/sneak/routewatch/internal/metrics"
 	"git.eeqj.de/sneak/routewatch/internal/ristypes"
-	"github.com/google/uuid"
 )
 
 const (
@@ -461,7 +460,6 @@ func (h *PrefixHandler) createLiveRoute(update prefixUpdate) *database.LiveRoute
 
 	// Create live route record
 	liveRoute := &database.LiveRoute{
-		ID:          uuid.New(),
 		Prefix:      update.prefix,
 		MaskLength:  maskLength,
 		IPVersion:   ipVersion,