sfm_webapp: default to Database view + sortable columns + inline waveform plot

Three UX upgrades to the main SFM webapp at /, all reinforcing the
'browse stored events' flow as the primary entry point:

1. Default section is now Database, not Live Device.  Most users land
   here to look at stored events; Live Device is opt-in (click the tab
   to talk to a unit).  Initial history + units fetch fires on first
   paint so the table is populated when the page loads.

2. History table columns are sortable.  Click any header to sort:
   timestamp, serial, per-channel PPV (Tran/Vert/Long), PVS, mic dB(L),
   project, client, type, key.  Default direction varies by column type
   (desc for numbers + timestamps, asc for text).  Sort arrows appear
   in the active column header.  Headers are sticky so they stay
   visible while scrolling.

3. Click-event-to-see-waveform.  The existing sidecar review modal now
   renders the 4-channel waveform plot inline at the top, fetched from
   /db/events/{id}/waveform.json in parallel with the sidecar fetch.
   Channels stacked MicL / Long / Vert / Tran (Instantel printout
   order), shared bottom time axis, dashed trigger line + triangle
   markers at t=0, zero baseline with "0.0" label on the right edge,
   peak callouts per channel.  Charts cleaned up on modal close.

Resolves the "where is the viewer" surprise — operators no longer need
to know about the /events route to see waveforms.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -8,7 +8,8 @@ All notable changes to seismo-relay are documented here.
 
 ### Added
 
-- **Stored-event browser** — new standalone HTML page at `GET /events` (`sfm/event_browser.html`).  Pick a serial from the unit dropdown, scroll through that unit's events (newest-first), click any event to render its decoded waveform via the existing `/db/events/{id}/waveform.json` endpoint.  Dark-themed Chart.js viewer, channels stacked vertically (Tran / Vert / Long / MicL — Instantel printout order, designed PDF-export-ready), trigger line at t=0, peak labels, search/filter, false-trigger flag honored.  Companion to the existing live-device viewer at `/waveform`; the two routes are now clearly delineated in their docstrings.
+- **SFM webapp now opens to Database view by default** and the History table is fully interactive.  Click any column header to sort ascending / descending (timestamp, serial, per-channel PPV, PVS, mic dB(L), project, client, record type, key — all sortable).  Click any event row to open the event modal, which now renders a **4-channel waveform plot inline** (MicL / Long / Vert / Tran stacked, Instantel-printout order) alongside the existing sidecar review fields.  Headers are sticky so the columns stay visible while scrolling long event lists.  No more "where is the viewer" — pick a unit from the filter dropdown, scan the table, click the event, see the waveform.
+- **Stored-event browser** — new standalone HTML page at `GET /events` (`sfm/event_browser.html`).  Pick a serial from the unit dropdown, scroll through that unit's events (newest-first), click any event to render its decoded waveform via the existing `/db/events/{id}/waveform.json` endpoint.  Dark-themed Chart.js viewer, channels stacked vertically (MicL / Long / Vert / Tran — Instantel printout order, designed PDF-export-ready), trigger line at t=0, peak labels, search/filter, false-trigger flag honored.  Companion to the existing live-device viewer at `/waveform`; the two routes are now clearly delineated in their docstrings.  The webapp's inline plot at `/` is the primary path; `/events` remains a useful diagnostic when you want just a viewer.
 - **Histogram body codec — uint8 peak count fix.**  Per-channel peak fields at `block[6]/[10]/[14]/[18]` are `uint8`, not `uint16 LE` spanning `block[6:8]` etc.  The original interpretation was byte-exact on the N844 fixture corpus only because every annotation byte (`block[7]/[11]/[15]/[19]`) in those fixtures was zero.  On non-N844 events with non-zero annotation bytes (observed across BE9558 Tran-drift and BE18003 Histogram+Continuous units), the old interpretation produced peaks up to 268 in/s per channel and 35× inflated PVS sums when first deployed to prod (rolled back same day; properly fixed in this release).  Cross-correlated against BW's per-interval ASCII export on K558 / T003 / N599 / N844 corpora — 100% byte-exact on T/V/L, 99%+ on M (sub-precision rounding).  Annotation byte preserved on each record as `record["annotations"]` for future RE.  Verified against ~3,500 blocks across 5 in-repo fixtures + a synthetic K558 interval-12 regression block.
 - **`apply_bw_report_dict_to_event` helper** in `minimateplus.event_file_io`.  Mirror of `apply_report_to_event` for the projected sidecar dict shape — used by the backfill path, which has the preserved `bw_report` block but not the original `.TXT` file.  BW's reported peaks (and `sample_rate` / `record_time`) now win over codec output during `--force` backfill, matching ingest-path behavior.
 - **`scripts/check_bw_report_preservation.py`** — two-step snapshot/diff tool to verify that `backfill_sidecars.py` doesn't wipe the `bw_report` block from existing sidecars.  Classifies every sidecar as PRESERVED / CHANGED / WIPED / STILL_MISSING / NEW / ADDED / REMOVED.  Exit code 1 if any WIPED or CHANGED entries are found, so it can gate a CI step or deploy script.