fix(#240): remove CTA buttons and dead i18n keys from Mission Control Strip

The enrich page already handles task routing; the buttons in the
segmentation and transcription columns were redundant. Removes the
unused mission_control_segmentation_cta, mission_control_transcription_cta,
and mission_control_ready_all_cta keys from all three locale files.

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

frontend/messages/en.json

@@ -562,17 +562,14 @@
 	"mission_control_segmentation_heading": "Draw regions",
 	"mission_control_segmentation_description": "Mark text areas — no prior knowledge needed",
 	"mission_control_seg_skill_pill": "✓ No prior knowledge",
-	"mission_control_segmentation_cta": "Start marking →",
 	"mission_control_segmentation_empty": "All documents already have segmentation blocks.",
 	"mission_control_transcription_heading": "Type the text",
 	"mission_control_transcription_description": "Type out text — Kurrent knowledge helpful",
 	"mission_control_trans_skill_pill": "Kurrent helpful",
-	"mission_control_transcription_cta": "Start typing →",
 	"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_subtitle": "{count} documents ready",
-	"mission_control_ready_all_cta": "Read all {count} →",
 	"mission_control_ready_empty": "No documents fully transcribed yet.",
 	"mission_control_ready_empty_cta": "Start contributing",
 	"mission_control_weekly_pulse": "↑ +{count} this week",