feat: add connected Grinder domain and API (#889)

[ODevStudio]

Summary

• Add the transport-independent GrinderDevice domain and one selected connected grinder, using the existing plugin session/readiness lifecycle for both BLE-backed and network-created devices.
• Add capability-gated operations, strict typed snapshots, generic device connection handling, and preferredGrinderDeviceId settings/backup support.
• Add singular connected-grinder REST routes and a controller-bound snapshot WebSocket that survives disconnect/replacement; update API specs and documentation.
• Cover both plugin paths with a shared contract suite and regressions for disconnect targeting, pending connection cancellation, snapshot adoption, and stale teardown completion.

Linked Issue

Fixes #889

Part of #890 (0.9.0 execution tracker): implements P0 release gate 2, the connected Grinder domain/API. The other release gates remain separate work.

Verification

• flutter analyze: no issues found.
• flutter test: 4,333 passed, 1 skipped.
• Shared fake BLE/network Grinder contracts cover readiness, capabilities, sessions, inventory, generic connection, REST, and WebSocket replacement.
• Running Windows app in simulated mode: inventory, connect, info/state, start/stop, setting, RPM, and disconnect returned expected responses; info returned 503 after disconnect.
• The same live WebSocket stayed open across plugin v1-to-v2 replacement and resumed with the replacement's snapshot (5 to 7 frames).
• Windows smoke used the installed VS2022/CMake 3.28 build toolchain because Flutter selected an older CMake 3.20 installation incompatible with Firebase's CMake 3.22 minimum. No tracked build configuration was changed for the workaround.
• git diff --check: clean. Temporary smoke plugin and runtime processes were removed. No physical grinder was required.

Impact

• Adds /api/v1/grinder/info, /api/v1/grinder/state, state start/stop PUTs, setting/RPM PUTs, and /ws/v1/grinder/snapshot.
• Runtime deviceId and preferredGrinderDeviceId remain separate from persisted Grinder UUIDs and workflow grinderId. Existing plural /api/v1/grinders CRUD and the persisted Grinder model are unchanged.
• Uses existing generation/session fencing and transport permission boundaries. Unknown/vendor snapshot fields and unsupported controls are rejected.
• Includes no production drivers, presets, workflow synchronization, multiple selected grinders, or new scanner/reconnect scheduler. No database migration or new dependency.
• Design rationale is archived in doc/plans/archive/connected-grinder/design.md; the temporary implementation plan was removed.

Contributor Responsibility

AI-assisted development is allowed. The submitter remains responsible for the submitted work. This draft leaves the personal attestation below for the human submitter to confirm.

• I have reviewed and understand all changes in this PR and take responsibility for their correctness, security, behavior, licensing, and provenance, including any AI-assisted or AI-generated work.