Meters: add manual reading entry from the meter-detail Readings tab

Entering a reading by hand previously meant POST /api/v1/readings with an
API key, or a one-row CSV through the import wizard. SourceType.Manual
existed in the enum but nothing was behind it. This adds the click path,
built for the case it is actually used in: walking to each manual meter
with a phone in hand.

"Add reading" on the Readings tab opens a dialog prefilled with the
meter's last register value and the current local time, both editable:

- An on-screen keypad, because a register is read standing at the meter.
  It behaves like a calculator against the prefill - the first digit
  replaces it (a fresh register), while backspace edits it in place,
  which is the common case since only a register's last digits move.
- Typed input accepts both separators (last one wins), so a German and
  an English phone keyboard both do the right thing. ReadingEntry owns
  that rule and is unit-tested; it deliberately differs from
  GermanNumber, where a lone dot really is a thousands separator.
- A live parsed-value echo plus delta-since-last, which is the net that
  catches a mistyped digit before it is committed.
- Decrease / replaces-existing / future / backdated surfaced before
  saving, and DST spring-forward gaps refused rather than shifted.

The verdict line sits in a fixed-height, no-wrap slot above the keypad.
That is load-bearing, not cosmetic: an alert that appears there when the
value dips below the last reading moves the keys out from under the
user's thumb mid-entry, which is a guaranteed mistype on a phone. The
long-form explanation goes below the keypad, where reflow is harmless.

Saving goes through IngestionService.IngestByMeterAsync, so the
monotonic-decrease guard and inline renormalization apply exactly as for
any other ingest. A new optional quality parameter stamps the row
ReadingQuality.Manual; null preserves today's behaviour, so a source
re-reporting the same timestamp updates the value without silently
relabelling a hand-entered or imported reading.

Also: the meter-detail tabs now render times in the instance timezone
per SDD section 10, instead of raw UTC. Without it a reading entered at
18:00 reads back as 16:00. Side effect is that historic imported monthly
rows show 01:00/02:00 rather than 00:00 - correct, if noisier.

Claude-Session: https://claude.ai/code/session_01D4x3JbNKCSV4cBR9s7bJmX

src/Infrastructure/Ingestion/IngestionService.cs

@@ -56,21 +56,26 @@ public sealed class IngestionService(
             return IngestionOutcome.RejectedDecrease;
         }
 
-        var outcome = await UpsertAsync(meter, utc, value, source.Id, cancellationToken).ConfigureAwait(false);
+        var outcome = await UpsertAsync(meter, utc, value, source.Id, quality: null, cancellationToken).ConfigureAwait(false);
         await UpdateSourceStatusAsync(source, utc, value, "ok", cancellationToken).ConfigureAwait(false);
         await RenormalizeAsync(meter.Id, outcome, cancellationToken).ConfigureAwait(false);
         return outcome;
     }
 
-    /// <summary>Ingests directly against a meter (REST push, e.g. Home Assistant POST /api/v1/readings).</summary>
+    /// <summary>Ingests directly against a meter (REST push, or a hand-entered reading from the UI).</summary>
     /// <param name="renormalize">
     /// False to skip deriving consumption, for callers ingesting a batch into one meter: recomputing
     /// rewrites the meter's entire series, so doing it per reading is quadratic in batch size. Such a
     /// caller must recompute the affected meters itself once the batch is in.
     /// </param>
+    /// <param name="quality">
+    /// Provenance to stamp on the row. Null keeps the default for a new row and leaves an existing
+    /// row's quality alone — a source re-reporting a timestamp must not silently relabel a reading
+    /// somebody entered by hand or that came from an import.
+    /// </param>
     public async Task<IngestionOutcome> IngestByMeterAsync(
         int meterId, DateTimeOffset time, double value, bool renormalize = true,
-        CancellationToken cancellationToken = default)
+        ReadingQuality? quality = null, CancellationToken cancellationToken = default)
     {
         var meter = await _db.Meters
             .FirstOrDefaultAsync(m => m.Id == meterId, cancellationToken).ConfigureAwait(false);
@@ -86,7 +91,7 @@ public sealed class IngestionService(
             return IngestionOutcome.RejectedDecrease;
         }
 
-        var outcome = await UpsertAsync(meter, utc, value, sourceId: null, cancellationToken).ConfigureAwait(false);
+        var outcome = await UpsertAsync(meter, utc, value, sourceId: null, quality, cancellationToken).ConfigureAwait(false);
         await _db.SaveChangesAsync(cancellationToken).ConfigureAwait(false);
         if (renormalize)
         {
@@ -161,7 +166,8 @@ public sealed class IngestionService(
     }
 
     private async Task<IngestionOutcome> UpsertAsync(
-        Meter meter, DateTimeOffset utc, double value, int? sourceId, CancellationToken cancellationToken)
+        Meter meter, DateTimeOffset utc, double value, int? sourceId, ReadingQuality? quality,
+        CancellationToken cancellationToken)
     {
         var existing = _db.Readings.Local.FirstOrDefault(r => r.MeterId == meter.Id && r.Time == utc)
             ?? await _db.Readings.FirstOrDefaultAsync(r => r.MeterId == meter.Id && r.Time == utc, cancellationToken).ConfigureAwait(false);
@@ -174,13 +180,18 @@ public sealed class IngestionService(
                 Time = utc,
                 Value = value,
                 SourceId = sourceId,
-                Quality = ReadingQuality.Measured,
+                Quality = quality ?? ReadingQuality.Measured,
             });
             return IngestionOutcome.Written;
         }
 
         existing.Value = value;
         existing.SourceId = sourceId ?? existing.SourceId;
+        if (quality is { } stamp)
+        {
+            existing.Quality = stamp;
+        }
+
         return IngestionOutcome.Updated;
     }