feat: cover seedlings (plantón) in copy + legal, backup cadence, server picker

Beta-tester feedback triage. The data model already had LotType.seedling as
first class; the gaps were copy and UX.

- Seedlings/plantones: broaden landing hero (EN/ES), in-app legal notice, and
  all legal texts (site + docs masters) from seeds-only to "seeds and
  seedlings", with a live-plant phytosanitary/transport caveat. Seeds stay the
  hero — targeted, not a blanket rename.
- Backups: settings line now states the 7-day cadence explicitly; cadence lives
  in AutoBackupService.backupInterval as the single source for text and schedule.
- Community servers: replace the manual wss:// text box with a checklist of the
  known servers (defaults visible/toggleable) plus an "add server" affordance
  with basic validation. No jargon in the UI.

i18n across en/es/pt/fr/de/ast (ja falls back). Tests updated + a new
server-picker widget test.

apps/app_seeds/lib/i18n/en.i18n.json

@@ -106,8 +106,8 @@
  "backup": {
   "title": "Backup & restore",
   "autoBackupTitle": "Automatic backups",
-  "autoBackupLast": "Last copy saved {date}",
-  "autoBackupNone": "A copy is kept automatically in the background",
+  "autoBackupLast": "Last copy saved {date} · every {days} days",
+  "autoBackupNone": "A copy is kept automatically every {days} days",
   "exportJson": "Save a backup",
   "exportJsonSubtitle": "A complete copy to keep safe, restore later or move to another device",
   "importJson": "Restore a backup",
@@ -524,8 +524,10 @@
   "areaCodeLabel": "Area code",
   "areaCodeHint": "A short code like sp3e9 — not a place name",
   "serversLabel": "Community servers",
-  "serversHelp": "One address per line (wss://…). Leave the defaults if unsure.",
+  "serversHelp": "Choose which servers to use. Leave the defaults if unsure.",
   "serversAdvanced": "Add another server",
+  "serverAddress": "Server address",
+  "serverInvalid": "Enter a valid address (wss://…)",
   "save": "Save",
   "saved": "Saved",
   "wanted": "Wanted",
@@ -708,8 +710,8 @@
   "privacyBody": "Tane works without an account, and everything you record stays on your device, encrypted. There are no ads, no trackers, and no Tane server.\n\nNothing is shared unless you choose to: when you publish an offer or your profile, or send a message, it travels through community-run servers. Offers only ever carry a rough zone — never your address.\n\nWhat you publish is public, and copies may remain even after you remove it — so share with care.",
   "rulesTitle": "Rules of the road",
   "rulesBody": "Tane is a tool, not a shop: exchanges are agreed directly between people, and nobody takes a cut. That also means you are responsible for what you offer and send.\n\nIn the market: be honest about your seeds, only offer what you may share, treat people well, and don't spam. You can block anyone, and report offers or people that break the rules — reports are acted on in the community servers.",
-  "seedsTitle": "About sharing seeds",
-  "seedsBody": "Gifting and swapping seeds between amateurs is broadly recognized in most countries. Selling can be different: in many places, selling seed of varieties that aren't officially registered is restricted — check your local rules before asking a price.\n\nSending seeds to another country is often restricted too, and commercially protected varieties must not be propagated without permission. When in doubt, keep it local and keep it a gift.",
+  "seedsTitle": "About sharing seeds and seedlings",
+  "seedsBody": "Gifting and swapping seeds between amateurs is broadly recognized in most countries. Selling can be different: in many places, selling seed of varieties that aren't officially registered is restricted — check your local rules before asking a price.\n\nSending seeds to another country is often restricted too, and commercially protected varieties must not be propagated without permission. When in doubt, keep it local and keep it a gift.\n\nThe same spirit applies to seedlings and young plants, but live plants can carry stricter transport and plant-health rules than seeds — moving them across regions or borders may need extra checks.",
   "readFull": "Read the full documents online"
  },
  "marketGate": {