Show every time in US Eastern (America/New_York)

Webapp: config.DISPLAY_TZ (default America/New_York) and a local_dt
filter that renders datetimes, ISO strings and Unix timestamps as e.g.
"2026-10-05 13:54 EDT", DST included. Used for the ServiceNow tick list,
technician to-do, imaging tiles and detail page; timestamp_fmt (reports,
backups, enrollment) goes through it too instead of relying on the
process TZ. CSV report_date is Eastern with its offset. Evidence-pack
months are Eastern calendar months, so a wipe late on the 31st lands in
that month rather than the next.

Blancco: init points the new root's /etc/localtime at America/New_York
so the GUI clock is local. Report timestamps keep their explicit
offset; report.utc_offset stays 0 since a fixed offset cannot follow DST.
Report file names stay UTC, as Blancco's own Save names them.

webapp/config.py

@@ -25,6 +25,9 @@ IMAGING_DIR = os.environ.get("IMAGING_DIR", "/var/log/pxe-imaging")
 # small JSON state file (cloud-upload confirmations, ServiceNow ticks) kept
 # off the report share so it never shows up as a report.
 BLANCCO_SITE = os.environ.get("BLANCCO_SITE", "West Jefferson")
+# Every time the webapp shows (and evidence-pack month boundaries) is in
+# this zone, DST included. Stored timestamps keep their own UTC offsets.
+DISPLAY_TZ = os.environ.get("DISPLAY_TZ", "America/New_York")
 BLANCCO_STATE = os.environ.get("BLANCCO_STATE", "/var/lib/pxe-webapp/blancco-state.json")
 
 # Log sources used by services/imaging_log_tail.py to infer client progress