Add custom output IDs and harden source configuration and calculations

[softwarecrash]

Summary

This PR improves SourceAnalytix source configuration, output ID handling, cumulative meter reset detection, calculation stability and per-source rounding settings.

Changes

Custom output IDs

• Adds an editable output ID for every configured source.
• Pre-fills the field with the existing source-derived ID for backward compatibility.
• Supports shorter IDs containing letters, numbers, underscores and hyphens.
• Validates reserved, invalid and duplicate output IDs before saving.
• Migrates an existing generated object tree when the output ID changes.
• Copies and verifies the complete tree before removing the previous output.
• Keeps the source name separate from its technical output ID.

Source configuration validation

• Validates required price definitions, units and output IDs directly in the custom settings.
• Disables saving while required settings are invalid when supported by the Admin adapter.
• Remains compatible with older Admin versions that do not support blocking root validation.

Cumulative meter resets

• A large decrease is now treated as a reset candidate first.
• The reset is confirmed only when a following reading remains in the lower range.
• Temporary zero or low readings are discarded when the meter returns to its previous range.
• Confirmed resets and replacement meters continue from the previous cumulative total.
• Small backwards fluctuations remain covered by the configured threshold.

Calculation stability

• Keeps a stable source state snapshot while asynchronous calculations are running.
• Prevents configuration updates or object changes from invalidating an active calculation.

Explicit rounding settings

• Every source now stores explicit decimal settings for consumption and cost values.
• New sources are pre-filled from the configured instance templates.
• Existing sources without these fields are migrated once to their previously effective values.
• Later changes to the instance templates no longer alter existing sources.
• -1 continues to store exact values without rounding.
• Invalid legacy values are normalized consistently in both the Admin UI and backend.

Documentation and tests

• Updates the README for output IDs, meter reset confirmation and rounding behavior.
• Adds coverage for output ID validation and migration helpers.
• Adds tests for transient meter readings, confirmed resets and replacement meters.
• Adds tests for source-specific rounding defaults and legacy value normalization.
• Updates all included translations.

Closes #617
Closes #1198
Closes #1199
Closes #1202