release: v0.13.1 — mic chart defaults to psi (matches PDF)

v0.13.0 shipped the mic_unit_pref default as "dBL", which made the
website chart's mic axis inconsistent with the PDF report (which
renders psi).  Original brief was always "psi on charts, dBL on
peaks" — I implemented the default backwards.  Operator caught it
within an hour of rollout.

Same-day patch:
- backend/models.py: default "dBL" → "psi"
- migrate_add_mic_unit_pref.py: idempotent across both fresh DB
  ("add column with psi default") and v0.13.0 upgrade ("flip dBL
  rows to psi").  One-row table, freshness assumed.
- backend/routers/settings.py: GET/PUT fallback "dBL" → "psi"
- templates/settings.html: dropdown's `selected` flag moves to psi
  + reorders options + relabels with "(matches PDF report)" hint
- backend/static/event-modal.js: module-level fallback + branch
  conditions flip to make psi the unset/error default

Includes the "Captured at" → "Time received" relabel from earlier
in the day (already-shipped commit 43c804d) rolled into the
release notes.

Migration is idempotent + safe to re-run; rolled out on the dev
container during this commit's smoke test.

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

backend/migrate_add_mic_unit_pref.py

@@ -3,10 +3,19 @@
 Database migration: Add mic_unit_pref column to user_preferences.
 
 Adds a single field controlling the mic channel's unit on the event-
-report waveform chart in the SFM event detail modal.  "dBL" (default)
-or "psi".  Peaks and KPI tiles elsewhere are always dBL regardless.
+report waveform chart in the SFM event detail modal.  "psi" (default —
+matches the PDF report's mic axis) or "dBL".  Peaks and KPI tiles
+elsewhere are always dBL regardless.
 
-Idempotent — safe to re-run.
+History: v0.13.0 originally shipped this with default "dBL", which
+made the website chart inconsistent with the PDF.  v0.13.1 flips the
+default to "psi" so they match.  This migration is idempotent and
+covers three cases:
+
+1. Fresh DB without the column — adds it with default 'psi'.
+2. DB upgraded from v0.13.0 (column exists, value 'dBL') — flips to
+   'psi' on the assumption no operator deliberately picked 'dBL' yet.
+3. DB upgraded from later — flip step is a no-op for non-'dBL' values.
 """
 
 import sqlite3
@@ -32,24 +41,33 @@ def migrate():
     cur.execute("PRAGMA table_info(user_preferences)")
     existing = {row[1] for row in cur.fetchall()}
 
-    if "mic_unit_pref" in existing:
-        print("mic_unit_pref already exists — nothing to do.")
-        conn.close()
-        return
+    if "mic_unit_pref" not in existing:
+        cur.execute(
+            "ALTER TABLE user_preferences "
+            "ADD COLUMN mic_unit_pref TEXT DEFAULT 'psi'"
+        )
+        # Backfill any rows where the column ended up NULL.
+        cur.execute(
+            "UPDATE user_preferences SET mic_unit_pref = 'psi' "
+            "WHERE mic_unit_pref IS NULL"
+        )
+        print("Added mic_unit_pref column (default 'psi').")
+    else:
+        print("mic_unit_pref column already exists.")
+
+    # v0.13.0 → v0.13.1 default-flip: rows still sitting at the original
+    # 'dBL' default get bumped to 'psi'.  If any operator deliberately
+    # chose 'dBL' through Settings before this migration runs they'd
+    # get reset — acceptable trade-off given the small user base and
+    # the fact the setting is one click to restore.
+    cur.execute("UPDATE user_preferences SET mic_unit_pref = 'psi' "
+                "WHERE mic_unit_pref = 'dBL'")
+    flipped = cur.rowcount
+    if flipped:
+        print(f"Flipped {flipped} row(s) from 'dBL' to 'psi' (v0.13.0 default).")
 
-    cur.execute(
-        "ALTER TABLE user_preferences "
-        "ADD COLUMN mic_unit_pref TEXT DEFAULT 'dBL'"
-    )
-    # Backfill the single row that should exist (id=1) to the default,
-    # in case the column ends up NULL on existing rows.
-    cur.execute(
-        "UPDATE user_preferences SET mic_unit_pref = 'dBL' "
-        "WHERE mic_unit_pref IS NULL"
-    )
     conn.commit()
     conn.close()
-    print("Added mic_unit_pref to user_preferences (default 'dBL').")
 
 
 if __name__ == "__main__":