feat(alarms): HiLo trigger type with per-band level, hysteresis, messages, overrides

Adds a new HiLo alarm trigger type with four configurable setpoints
(LoLo / Lo / Hi / HiHi). Each setpoint carries an optional priority,
deadband (for hysteresis), and operator message. The site runtime emits
AlarmStateChanged with an AlarmLevel field so consumers can differentiate
warning vs critical bands.

Plumbing:
  - new AlarmLevel enum + AlarmStateChanged.Level/Message init properties
  - AlarmTriggerEditor (Blazor) gets a HiLo render with severity tinting
  - AlarmTriggerConfigCodec extracted from the editor for testability
  - sitestream.proto carries level + message over gRPC
  - SemanticValidator enforces numeric attribute, setpoint ordering,
    non-negative deadband
  - on-trigger scripts get an Alarm global (Name/Level/Priority/Message)
    so notification routing can branch by severity
  - per-instance InstanceAlarmOverride entity + EF migration + flattening
    step + CLI commands; HiLo overrides merge setpoint-by-setpoint, binary
    types whole-replace
  - DebugView shows a Level badge + per-band message tooltip
  - App.razor auto-reloads on permanent Blazor circuit failure
  - docker/regen-proto.sh automates the proto regen workflow (the linux/arm64
    protoc segfault means generated files are checked in for now)

docs/requirements/HighLevelReqs.md

@@ -106,16 +106,18 @@ Each alarm has:
 - **Priority Level**: Numeric value from 0–1000.
 - **Lock Flag**: Controls whether the alarm can be overridden downstream.
 - **Trigger Definition**: One of the following trigger types:
-  - **Value Match**: Triggers when a monitored attribute equals a predefined value.
+  - **Value Match**: Triggers when a monitored attribute equals a predefined value. Supports a `!=X` prefix on the match value for not-equals semantics.
   - **Range Violation**: Triggers when a monitored attribute value falls outside an allowed range.
-  - **Rate of Change**: Triggers when a monitored attribute value changes faster than a defined threshold.
+  - **Rate of Change**: Triggers when a monitored attribute value changes faster than a defined threshold over a configurable time window. A direction filter (rising / falling / either) restricts which side of the rate triggers.
+  - **HiLo**: Multi-setpoint level alarm. Any subset of four setpoints (LoLo, Lo, Hi, HiHi) may be configured. The most severe matching band wins (LoLo/HiHi outrank Lo/Hi). Each setpoint may carry its own priority that overrides the alarm-level priority for that band.
 - **On-Trigger Script** *(optional)*: A script to execute when the alarm triggers. The alarm on-trigger script executes in the context of the instance and can call instance scripts, but instance scripts **cannot** call alarm on-trigger scripts. The call direction is one-way.
 
 ### 3.4.1 Alarm State
 - Alarm state (active/normal) is **managed at the site level** per instance, held **in memory** by the Alarm Actor.
+- Active alarms additionally carry an **alarm level**: `None` for binary trigger types (ValueMatch, RangeViolation, RateOfChange); one of `Low`, `LowLow`, `High`, `HighHigh` for HiLo triggers based on which setpoint the monitored attribute has crossed. Level transitions within an active HiLo alarm (e.g., High → HighHigh) emit fresh state-change events without re-running the on-trigger script — the script only fires on the Normal → non-None edge.
 - When the alarm condition clears, the alarm **automatically returns to normal state** — no acknowledgment workflow is required.
 - Alarm state is **not persisted** — on restart, alarm states are re-evaluated from incoming values.
-- Alarm state changes are published to the site-wide Akka stream as `[InstanceUniqueName].[AlarmName]`, alarm state (active/normal), priority, timestamp.
+- Alarm state changes are published to the site-wide Akka stream as `[InstanceUniqueName].[AlarmName]`, alarm state (active/normal), alarm level, priority, timestamp.
 
 ### 3.5 Template Relationships