feat(deepinfra): add DeepInfra API usage provider (0.45 port)

[Finesssee]

Summary

Port DeepInfra billing/usage provider from upstream steipete/CodexBar into the Windows Rust backend and Tauri UI wiring.

DeepInfra is API-key only. CodexBar queries DeepInfra's documented billing endpoints and never sends model prompts or account data to third parties.

Endpoints

Method	URL	Purpose
GET	https://api.deepinfra.com/payment/checklist?compute_owed=true	Prepaid balance (stripe_balance), recent spend, spending limit, suspension
GET	https://api.deepinfra.com/payment/usage?from=current	Current-month spend (total_cost in cents)

Auth: Authorization: Bearer <api_key>

Balance semantics (match upstream)

• Negative stripe_balance = prepaid funds; convert to positive available after deducting recent
• Positive net balance = amount owed
• Monthly usage cents → USD via /100
• Spending limit only applied when limit > 0
• Suspended accounts reported as 100% used with reason text

Credentials

• Preferences API key store / Windows Credential Manager (codexbar-deepinfra)
• Env: DEEPINFRA_API_KEY (primary), DEEPINFRA_TOKEN (fallback)
• Multi-key token accounts inject DEEPINFRA_API_KEY

Changes

• New rust/src/providers/deepinfra/mod.rs with parse/fetch + fixture unit tests
• Register ProviderId::DeepInfra in provider.rs, provider_factory.rs, providers/mod.rs
• API key catalog + credential migration + token accounts
• UI: icon SVG, registry, catalog, dashboard/status sets, API source label

Tests run

cargo test --manifest-path rust/Cargo.toml deepinfra
# 6 passed

cargo test --manifest-path rust/Cargo.toml every_provider_id_is_instantiable
# 1 passed

Notes / gaps vs upstream

• Widget support still n/a (upstream also marks DeepInfra unsupported in widgets)
• No live network tests (fixture-only, same as other API-key ports)
• Per-request cost history still unavailable (matches upstream supportsTokenCost: false)

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