feat(#240): Mission Control Strip frontend — 5 components + dashboard wiring

Adds the full-width 3-column collaboration widget below the existing
dashboard grid. Renders without the backend running (Promise.allSettled
isolation keeps failures silent).

Components (src/lib/components/):
- ExpertBadge.svelte — purple pill with icon, no props
- SegmentationColumn.svelte — col 1: links to /enrich/{id}, weekly pulse
- TranscriptionColumn.svelte — col 2: per-doc progress bar when blocks exist
- ReadyColumn.svelte — col 3: mint border when filled, dashed empty state
- MissionControlStrip.svelte — strip wrapper, 1-col mobile / 3-col sm+

i18n: 19 new keys added to de/en/es (mission_control_*)

Page wiring:
- +page.server.ts: 4 new Promise.allSettled calls for segmentation-queue,
  transcription-queue, ready-to-read, weekly-stats; all failures silent
- +page.svelte: MissionControlStrip rendered below the grid in isDashboard

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/messages/en.json

@@ -555,5 +555,22 @@
 	"training_seg_too_few_blocks": "At least 5 segmentation blocks required (currently: {available}).",
 	"transcription_block_segmentation_only": "Segmentation only",
 	"training_chip_kurrent": "Kurrent recognition",
-	"training_chip_segmentation": "Segmentation"
+	"training_chip_segmentation": "Segmentation",
+	"mission_control_heading": "Contribute",
+	"mission_control_segmentation_heading": "Segmentation",
+	"mission_control_segmentation_description": "Mark text areas — no prior knowledge needed",
+	"mission_control_segmentation_cta": "Segment",
+	"mission_control_segmentation_empty": "All documents already have segmentation blocks.",
+	"mission_control_transcription_heading": "Transcription",
+	"mission_control_transcription_description": "Type out text — Kurrent knowledge helpful",
+	"mission_control_transcription_cta": "Transcribe",
+	"mission_control_transcription_empty": "No documents waiting for transcription.",
+	"mission_control_ready_heading": "Ready to Read",
+	"mission_control_ready_description": "Fully transcribed and reviewed",
+	"mission_control_ready_empty": "No documents fully transcribed yet.",
+	"mission_control_ready_empty_cta": "Start contributing",
+	"mission_control_weekly_pulse": "↑ +{count} this week",
+	"mission_control_expert_badge": "Expert needed",
+	"mission_control_blocks_progress": "{texted} / {total} blocks",
+	"mission_control_reviewed_pct": "{pct}% reviewed"
 }