feat(ux): add CTAs to EmptyState across screens (issue #618) (#627)

Turn dead-end empty states into on-ramps by wiring the existing
EmptyState actionLabel/onAction params to real next actions.

Screens wired (real, existing actions):
- Skills (installed): Browse skill hub -> setViewMode(HUB)
- Skills (hub): Retry search -> searchHub(hubQuery)
- Cron Jobs: Create your first job -> openNewJobDialog()
- MCP servers: Add a server -> toggleAddForm() (literal moved to strings.xml)
- Webhooks: Create subscription -> showCreateDialog() (literal moved to strings.xml)
- Channels: Connect a Telegram channel -> startTelegramOnboarding()
- Model: Configure model -> navigateTo(SettingsConnection)
- Sessions (history): Start a new chat -> navigateTo(ChatScreen)
- Analytics: Explore Skills or Cron jobs -> navigateTo(SkillsScreen)
- Keys (no match): Clear search -> query = ""

All new labels use strings.xml (empty_action_* / screenname_empty_*).

Deviations from issue (documented honestly):
- Toolsets, Profiles, Plugins keep Refresh. No in-app create path exists
  (toolsets are server-defined toggles; profiles/plugins have no create
  dialog wired in UI). Refresh is the correct recovery there, not a fake
  'create' CTA. Flagged for follow-up if create flows get built.
- Skills: edited the real private InstalledSkillsView in SkillsScreen.kt;
  the duplicate internal one in InstalledSkillsTab.kt is dead code.

Verified: ktlintCheck clean, assembleDebug green.

Co-authored-by: M57 <hy4ri@users.noreply.github.com>
Co-authored-by: Ronia <ronia@hermes>

app/src/main/java/com/m57/hermescontrol/ui/webhooks/WebhooksScreen.kt

@@ -341,7 +341,7 @@ fun WebhooksScreen(
                             EmptyState(
                                 title =
                                     if (state.subscriptions.isEmpty()) {
-                                        "No subscriptions"
+                                        stringResource(R.string.webhooks_empty_title)
                                     } else {
                                         stringResource(R.string.webhooks_no_matching)
                                     },
@@ -351,6 +351,18 @@ fun WebhooksScreen(
                                     } else {
                                         stringResource(R.string.webhooks_no_matching_desc)
                                     },
+                                actionLabel =
+                                    if (state.subscriptions.isEmpty()) {
+                                        stringResource(R.string.webhooks_action_add)
+                                    } else {
+                                        null
+                                    },
+                                onAction =
+                                    if (state.subscriptions.isEmpty()) {
+                                        { viewModel.showCreateDialog() }
+                                    } else {
+                                        null
+                                    },
                             )
                         }
                     } else {