refactor(sensorservice): introduce measurement foundations

[Foxpace]

Introduces the models and state holders that define a measurement session independently of the service UI.

What was added

• Measurement launch requests and an intent factory.
• Session state and a central session store.
• A typed SensorSpec model and validation tests.
• Updated GPS, storage, manifest, strings, and sensor-holder error handling.
• Removal of obsolete power-management, audio, and placeholder test resources.

How it works

Callers construct a typed launch request, which the intent factory translates for the Android service boundary. The service and UI share session progress through the session store, and SensorSpec provides one normalized description of each requested sensor and sampling configuration.

Stack position

Layer 4 of 31 in the SensorBox refactor stack. Review this PR against its configured base to see only this layer.

Validation

• Full stack: ./gradlew test — BUILD SUCCESSFUL (160 tasks)

[Foxpace]

Superseded by #46, which targets master and shows the final current tree. Closing this stacked layer so review stays on the consolidated diff; this PR remains available as history.

[Foxpace]

Stack restored at the author's request. This PR is again part of the original 31-layer refactor chain. The architecture work continues as stacked PRs #47 through #54; consolidated PR #46 is superseded.