Meter chain topology + per-energy-type flow (Sankey) pages

Adds a meter hierarchy and a flow view: a downstream meter is a *subsection*
of an upstream one (not an addition), so you can see where a main meter's flow
divides — e.g. official water → garden, pool, other; grid/battery → all → car.

- MeterLink (schema + migration AddMeterLinks): a directed from→to flow edge.
  Multi-parent allowed (a merge, e.g. grid + solar → house); multi-child is a
  split. Cascade-deletes with either endpoint; unique + distinct-endpoint checks.
- FlowService: per energy type + period, builds a Sankey graph — nodes = meters
  sized by consumption; link value = downstream meter's consumption, split
  proportionally across multiple upstreams; unaccounted remainder under a meter
  becomes a synthetic "Other" node; depth via topological longest-path.
- SankeyChart.razor: hand-rolled inline-SVG Sankey (ApexCharts has no Sankey
  type) — columns by depth, nodes stacked by value, bezier ribbons sized by flow,
  left→right, theme-aware, HTML-encoded labels, tooltips. Built as a MarkupString
  to sidestep Razor's <text> element clash.
- /energy/{id} page (one per energy type): KPIs (consumption + cost), the flow
  Sankey, and the meter list. NavMenu now lists a link per energy type
  (Electricity, Water, Gas, …) loaded from the DB.
- Meters admin: cycle-safe "Sub-meter of (upstream meters)" multi-select
  (descendants excluded to prevent cycles); reconciles meter_link rows on save.
- Reference data seeds a demo chain (Haus → Auto) so electricity flow shows
  Haus dividing into Auto + Other.

Tests: FlowServiceTests (single-parent remainder; two-parent proportional
split); render test now asserts the flow chain + covers /energy/{id}. 69 Core +
47 Integration = 116 green. Live-verified: Haus 95,450 kWh → Auto 51,909 +
Other 43,541 (flow conserved), all 5 energy-type pages render.

Claude-Session: https://claude.ai/code/session_01Lz2RqAsnQhetqWNoCDfexK

CLAUDE.md

@@ -6,7 +6,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 MeterVault is a self-hosted, local-first energy & utility metering platform: it ingests meter data from Home Assistant, Tasmota and MQTT on a schedule, stores every reading timestamped and immutable, normalizes it into consumption, and turns it into cost dashboards. Energy types (electricity, water, heating oil, gas, …) and meters are **user-defined, never hardcoded**.
 
-**Status: implemented (M0–M7) + SDD §8 panels.** The full solution is built and green — five projects, ~108 tests, working Docker deploy. `docs/SDD.md` remains the design reference; the milestone map (§12) matches the git history (M0…M7 commits). The dedicated **PV/Solar** (`/solar`), **Oil/consumable** (`/consumables`) and **meter-detail** (`/meters/{id}`) views (SDD §8.4–§8.6) are implemented as read models in `Infrastructure/Dashboard` (`SolarService`, `ConsumableService`, `MeterDetailService`) — PV meters are found by `Mode == GenerationCounter` and grid/load meters by a `role` tag in `Meter.Meta` (`MeterRoles`/`MeterMeta`), so nothing is hardcoded by name. **Admin write-CRUD** (SDD §8.7) is implemented as MudBlazor inline-dialog pages: energy types, meters (+ recompute on mode/baseline change), a meter's ingest sources (meter-detail Sources tab), tariffs, cost categories + members, and connectors (`ingestion_endpoint`, secrets by env-var reference only). `/admin/settings` is a read-only effective-config view (settings are env-driven and reproducible, not DB-stored). **Home Assistant reading** is configured here: an HA connector (`BaseUrl` + `TokenEnv`) + an HA source (entity id) drives `HomeAssistantWorker`'s REST poll; `HaConnectionTester` powers the connector "Test connection" button. Remaining refinements (HA WebSocket *push* — REST poll works today; commit-arbitrary-CSV-from-UI needs a meter-mapping wizard; full de-DE UI-string localization) are noted at their commits. Set `MeterVault__SeedReferenceData=true` (compose: `METERVAULT_SEED=true`) for a one-command populated demo.
+**Status: implemented (M0–M7) + SDD §8 panels.** The full solution is built and green — five projects, ~108 tests, working Docker deploy. `docs/SDD.md` remains the design reference; the milestone map (§12) matches the git history (M0…M7 commits). The dedicated **PV/Solar** (`/solar`), **Oil/consumable** (`/consumables`) and **meter-detail** (`/meters/{id}`) views (SDD §8.4–§8.6) are implemented as read models in `Infrastructure/Dashboard` (`SolarService`, `ConsumableService`, `MeterDetailService`) — PV meters are found by `Mode == GenerationCounter` and grid/load meters by a `role` tag in `Meter.Meta` (`MeterRoles`/`MeterMeta`), so nothing is hardcoded by name. **Admin write-CRUD** (SDD §8.7) is implemented as MudBlazor inline-dialog pages: energy types, meters (+ recompute on mode/baseline change), a meter's ingest sources (meter-detail Sources tab), tariffs, cost categories + members, and connectors (`ingestion_endpoint`, secrets by env-var reference only). `/admin/settings` is a read-only effective-config view (settings are env-driven and reproducible, not DB-stored). **Home Assistant reading** is configured here: an HA connector (`BaseUrl` + `TokenEnv`) + an HA source (entity id) drives `HomeAssistantWorker`'s REST poll; `HaConnectionTester` powers the connector "Test connection" button. **Meter topology & flow**: `MeterLink` (a directed `from→to` edge; a downstream meter is a *subsection* of an upstream one, multi-parent allowed) drives a per-energy-type page `/energy/{id}` with a hand-rolled SVG **Sankey** (`SankeyChart.razor`, since ApexCharts has no Sankey type) computed by `FlowService` (link value = downstream consumption, split proportionally across multiple parents; unaccounted remainder → an "Other" node). Upstream meters are wired cycle-safely in the meter editor; the nav lists a link per energy type. Remaining refinements (HA WebSocket *push* — REST poll works today; commit-arbitrary-CSV-from-UI needs a meter-mapping wizard; full de-DE UI-string localization) are noted at their commits. Set `MeterVault__SeedReferenceData=true` (compose: `METERVAULT_SEED=true`) for a one-command populated demo.
 
 ## Source of truth