feat(studio): operator QoL — flow runnability, audit grouping, batch approvals, welcome celebration (v0.42.0)

Four UX threads stitched into one commit. Each pulls Studio
toward Stefan's "zero-learning-curve" goal — the feedback
that earned its own memory entry.

1. Flow-Runnability-Indikator
   ─────────────────────────
   The Flows tab now fetches `listFlows` and `listModules`
   in parallel. Each card compares the flow's
   `requiredCapabilities` against the installed-modules'
   capability set; rows with missing modules show a "Needs:
   text.extract@^0" red pill row beneath the path and have
   their Run button greyed out + tooltip
   "Install the missing modules first." Operators stop
   hitting Run → cryptic hub error → frustration.

2. Welcome-Checklist Celebration
   ─────────────────────────────
   Once all four checklist signals flip to done, an
   `_AllDoneCelebration` card replaces the bare
   "All four steps complete" + Hide button. Three concrete
   next-threads with action buttons: "Read the audit log",
   "Set up the daily Today story" (opens the Flows / Today
   doc inline via `_DocReaderSheet`), and "Build your own
   module" (opens the architecture doc). Operator who just
   got set up sees what to do next instead of an empty
   "what now?" feeling.

3. Audit-Page Time-Bucket Headers + Flow-Run Detail
   ────────────────────────────────────────────────
   The flat event list grows tiny "TODAY / YESTERDAY /
   EARLIER THIS WEEK / OLDER" section headers — bucket is
   computed in the operator's local timezone so an event at
   23:55 yesterday in Berlin doesn't end up in "today"
   because UTC happened to spill into a new day.
   Plus: the event-detail dialog gains a "View flow run"
   action when the picked event has a `flow_execution`. It
   opens a drill-down that lists every event in the
   already-fetched 100-event window sharing the same
   execution id, sorted ascending — the operator reads the
   run from step.started top to flow.completed bottom.

4. Approvals-Batch-Aktionen
   ────────────────────────
   Each pending approval card grows a checkbox. When ≥1
   selected, a floating action bar appears at the bottom
   with "N selected · Select all · Clear · Reject all ·
   Approve all". The parent loops sequentially through the
   per-record SDK calls so a partial failure produces
   "X done, Y failed" instead of a confusing all-or-nothing
   rollback. Reject prompts for a reason once and applies
   to the whole picked set.

13 new ARB keys cover the strings the four features
needed. Studio's tests stay green.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/l10n/app_en.arb

@@ -407,6 +407,50 @@
       "error": { "type": "String" }
     }
   },
+  "flowsMissingModulesLabel": "Needs:",
+  "flowsRunDisabledTooltip": "Install the missing modules first.",
+  "welcomeChecklistAllSetTitle": "You're set up.",
+  "welcomeChecklistAllSetBody": "Three threads to pull on next:",
+  "welcomeChecklistNextAuditTitle": "Read the audit log",
+  "welcomeChecklistNextAuditBody": "Every install, flow run, and approval lives in the hash-chained log. Open the Audit tab to see what your hub has been up to.",
+  "welcomeChecklistNextAuditButton": "Open Audit",
+  "welcomeChecklistNextTodayTitle": "Set up the daily Today story",
+  "welcomeChecklistNextTodayBody": "Run tools/today/propose.sh on a cron and the editorial card on the store auto-fills with operator-curated narratives.",
+  "welcomeChecklistNextTodayButton": "Open Today docs",
+  "welcomeChecklistNextModuleTitle": "Build your own module",
+  "welcomeChecklistNextModuleBody": "Generate a Rust+WASM scaffold with `fai new module <name>`. The module-sdk handles the WIT plumbing; you write a typed invoke.",
+  "welcomeChecklistNextModuleButton": "Read the docs",
+  "auditGroupToday": "TODAY",
+  "auditGroupYesterday": "YESTERDAY",
+  "auditGroupThisWeek": "EARLIER THIS WEEK",
+  "auditGroupOlder": "OLDER",
+  "auditEventViewFlowRun": "View flow run",
+  "auditFlowRunDialogTitle": "Flow run · {flow}",
+  "@auditFlowRunDialogTitle": { "placeholders": { "flow": { "type": "String" } } },
+  "auditFlowRunDialogSubtitle": "{n} {n, plural, =1{event} other{events}} for execution {execution}",
+  "@auditFlowRunDialogSubtitle": {
+    "placeholders": {
+      "n": { "type": "int" },
+      "execution": { "type": "String" }
+    }
+  },
+  "approvalsSelectAll": "Select all",
+  "approvalsClearSelection": "Clear",
+  "approvalsBatchSelected": "{n} selected",
+  "@approvalsBatchSelected": { "placeholders": { "n": { "type": "int" } } },
+  "approvalsBatchApprove": "Approve all",
+  "approvalsBatchReject": "Reject all",
+  "approvalsBatchApproveDoneToast": "{n} approvals approved.",
+  "@approvalsBatchApproveDoneToast": { "placeholders": { "n": { "type": "int" } } },
+  "approvalsBatchRejectDoneToast": "{n} approvals rejected.",
+  "@approvalsBatchRejectDoneToast": { "placeholders": { "n": { "type": "int" } } },
+  "approvalsBatchPartialFailure": "{ok} done, {failed} failed.",
+  "@approvalsBatchPartialFailure": {
+    "placeholders": {
+      "ok": { "type": "int" },
+      "failed": { "type": "int" }
+    }
+  },
   "flowsRunButton": "Run",
   "flowsRunningTitle": "Running {name}",
   "@flowsRunningTitle": { "placeholders": { "name": { "type": "String" } } },