fix: sync-freshness banner, burst validation, and UI/UX polish

[abdulsaheel]

Summary

• Fixes a persistent "last data is more than an hour behind" regression: the freshness signal (AppState.lastRecordAt) only ever read decoded_onehz's max timestamp (misses R10-lite historical records, which land in samples instead) and only ever refreshed once at app boot. Now reads the rec_ts_hw sync cursor (the same frontier RecordGate/backfill policies already trust) and refreshes on every successful persist via the existing onDataStored hook — covers foreground bursts, background/headless drains, and live-triggered stores uniformly, with no race window against the async commit.
• Makes HISTORY_END packet-count validation advisory instead of a hard gate. A mismatch used to discard the entire buffered chunk and re-request the same block forever — since every buffered record already passed frame-level CRC32 and the RecordGate plausibility check before reaching this point, a count mismatch (whose exact semantics on real hardware traffic aren't fully confirmed) was never real evidence of bad data. Added burstPacketCountMatches as a small pure/testable function plus regression tests covering the real failure shape observed in the field.
• Profile screen: real back button (migrated to AppScaffold), dropped ~6 decorative/meaningless icons from personal-info rows (Sex→heart, Height→activity, etc.) and the "Storage" section (static notice, no content).
• Today screen: fixed a list-reflow glitch where the freshness banner toggling on/off shifted every sibling's position in an unkeyed list, causing Flutter to remount and replay every entrance animation at once — added stable Keys. Weekly steps card relabeled with context ("Steps goal (week)").
• MetricRow (shared "label left, value right" row powering Sleep/Heart/Respiratory/Skin-temp trend lists): dropped the per-row leading icon (repetitive across a whole screen of rows) and fixed numeric clipping — value now shrinks via FittedBox instead of silently ellipsizing.
• Journey + Timeline screens merged into one multi-vital "lookback" (heart rate, HRV, resp, skin temp on one scrubbable chart, values hidden until touched).
• Workout-type icons (cardio/run/cycling/walk/swim/yoga/hiit/workout-other, from the newly-merged icons package) wired through a new shared lib/ui/workouts/workout_types.dart seam, replacing three divergent per-screen icon tables.
• Regenerated pubspec.lock against real git-ref dependencies (was accidentally committed with local path overrides baked in — CI has never actually tested this state since the regression landed).

Test plan

• flutter analyze clean (only the pre-existing glassBoxReadiness deprecation baseline)
• flutter test --concurrency=1 → 376/376 pass, including 4 new regression tests for the burst-validation fix
• Verified against real main-branch git-ref dependencies (not local path overrides) — matches what CI resolves
• On-device verification of the freshness fix pending (root-caused via a temporary in-app diagnostics screen, since removed, using real device sync-ledger dumps)