chore(routes): default packet_count_threshold=5 and clear multiplier=3x

Change the new-route defaults so the create modal, REST API, YAML
import, and preview helper pre-fill packet_count_threshold=5 instead
of 3, and bump the effective-clear auto-multiplier from 2x to 3x so
the default comfort bar tracks to 15 for a default threshold of 5.

Schema/model/cli/preview:
- schemas/routes.py: RouteCreate + RoutePreviewRequest
  packet_count_threshold default 3 -> 5 (clear_threshold stays None)
- models/route.py: Route INSERT default 3 -> 5 (clear_threshold stays
  nullable, no default)
- collector/cli.py: YAML import fallbacks 3 -> 5
- collector/routes.py: preview helper fallback 3 -> 5; module constant
  CLEAR_DEFAULT_MULTIPLIER 2 -> 3 (drives effective_clear_threshold)
- api/metrics.py: route_clear gauge help text 2x -> 3x

UI:
- web/spa/pages/routes.js: new-route modal pre-fills
  packet_count_threshold=5; placeholder shows 3x threshold; parseInt
  fallback 3 -> 5. clear_threshold field unchanged (clearing still
  sends null for the auto-tracking behaviour).

Docs:
- docs/routes.md defaults table: window_hours 24->48, threshold 3->5,
  clear (2x)->(3x), max_hop_span (unlimited)->8. Previous four
  entries now match the shipped defaults (some were stale from #316).
- docs/seeding.md YAML example: window_hours 24->48, threshold 3->5,
  commented clear_threshold example 10->15 with 3x note.

No migration: packet_count_threshold uses Python-side default= (no
server_default), so existing rows keep their stored values. Existing
routes with clear_threshold=NULL continue to track via the new 3x
multiplier at evaluation time.

docs/routes.md

@@ -17,10 +17,10 @@ Each route carries these knobs:
 | Field | Default | Description |
 | --- | --- | --- |
 | `match_width` | `1` | Path-hash prefix width in bytes (1/2/3). Higher widths disambiguate nodes that share a short public-key prefix. |
-| `window_hours` | `24` | Rolling lookback window for the live status card. |
-| `packet_count_threshold` | `3` | Distinct matching packets at/above which the route is `healthy`. "Distinct" is per underlying event, not per transmission — see [How health is evaluated](#how-health-is-evaluated) above. |
-| `clear_threshold` | _(2× threshold)_ | Comfort bar for the `clear`/`marginal` split. Omit/null to use twice the threshold. |
-| `max_hop_span` | _(unlimited)_ | Caps the position gap between the first and last matched node, to reject matches that wander too far. |
+| `window_hours` | `48` | Rolling lookback window for the live status card. |
+| `packet_count_threshold` | `5` | Distinct matching packets at/above which the route is `healthy`. "Distinct" is per underlying event, not per transmission — see [How health is evaluated](#how-health-is-evaluated) above. |
+| `clear_threshold` | _(3× threshold)_ | Comfort bar for the `clear`/`marginal` split. Omit/null to use three times the threshold. |
+| `max_hop_span` | `8` | Caps the position gap between the first and last matched node, to reject matches that wander too far. |
 | `reversible` | `true` | Also match the path in reverse direction. |
 | `enabled` | `true` | When `false`, the route is skipped by the evaluator and reports `unknown`/`no_coverage`. |
 

docs/seeding.md

@@ -126,9 +126,9 @@ routes:
     description: A140 corridor route
     visibility: community
     match_width: 1
-    window_hours: 24
-    packet_count_threshold: 3
-    # clear_threshold: 10      # optional; omit/null = 2x threshold
+    window_hours: 48
+    packet_count_threshold: 5
+    # clear_threshold: 15      # optional; omit/null = 3x threshold
     # max_hop_span: 8           # optional; omit/null = unlimited
     enabled: true
     reversible: true              # match both directions (A->B and B->A)