phsl / new-api

System settings forms that used flat dotted API keys (e.g.
`performance_setting.monitor_cpu_threshold`) with React Hook Form were
broken: RHF stores dotted paths as nested objects on update, while dirty
checks and submit comparisons still read flat keys from defaults. Users
could edit values but always saw "No changes to save".

Refactor affected sections to use nested Zod schemas and default values
for RHF, with explicit helpers to convert between nested form state and
flat API keys. Track a normalized baseline in refs for accurate change
detection and post-save resets.

Add `safeNumberFieldProps` to prevent native `<input type="number">`
from writing NaN into form state when cleared. NaN caused Zod validation
to fail silently and made the save button appear unresponsive. The
helper ignores non-finite updates so controlled inputs snap back to the
last valid value, matching legacy Semi InputNumber behavior.

Sections refactored for dotted-key handling:
- maintenance/performance-section
- models/grok-settings-card
- auth/passkey-section
- auth/oauth-section
- auth/section-registry (pass attachment_preference raw; normalize in section)

Sections migrated to safeNumberFieldProps:
- maintenance/performance-section
- models/grok-settings-card
- integrations/monitoring-settings-section
- integrations/payment-settings-section
- integrations/creem-product-dialog
- general/pricing-section (USD exchange rate)
- general/system-behavior-section
- content/dashboard-section

Optional numeric fields (e.g. custom currency exchange rate) keep their
existing empty-to-undefined semantics and are intentionally unchanged.