Refactor canvas storage URL handling and integrate adjustment presets

- Introduced a new `CanvasPresetsProvider` to manage adjustment presets for nodes, enhancing state management and reducing reactivity.
- Updated storage URL resolution to utilize a mutation instead of a reactive query, improving performance and reducing unnecessary re-renders.
- Refactored adjustment nodes (color-adjust, curves, detail-adjust, light-adjust) to use the new preset context for fetching user presets.
- Improved overall canvas functionality by streamlining storage ID collection and URL resolution processes.

docs/plans/2026-04-03-canvas-convex-load-shedding-design.md

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+# Canvas Convex Load Shedding Design
+
+## Goal
+
+Reduce Convex query fanout and hot-path load on the canvas page so node placement and canvas interaction no longer collapse when the local Convex runtime is under pressure.
+
+## Findings
+
+- `nodes:create` itself is fast when the runtime is healthy.
+- The canvas page issues multiple concurrent reactive queries: `nodes:list`, `edges:list`, `canvases:get`, `credits:getBalance`, `credits:getSubscription`, `storage:batchGetUrlsForCanvas`, and several `presets:list` variants.
+- During failure windows, many unrelated queries time out together, which points to runtime saturation rather than a single broken query.
+
+## Chosen Approach
+
+Use a broad load-shedding refactor on the canvas hot path:
+
+1. Remove debug-only and non-essential queries from the core canvas render path.
+2. Eliminate the server-side batch storage URL query by deriving stable fallback URLs client-side from `storageId`.
+3. Collapse multiple adjustment preset queries into one shared presets query and distribute the data through React context.
+4. Drop the subscription-tier query from the canvas toolbar and keep the toolbar credit widget on the cheaper balance path only.
+
+## Expected Impact
+
+- Fewer unique Convex subscriptions on the canvas page.
+- Less full-canvas invalidation work after every node or edge mutation.
+- Lower pressure on `auth:safeGetAuthUser` because fewer canvas-adjacent queries depend on it.
+- Better resilience when Convex dev runtime is temporarily slow.
+
+## Risks
+
+- Client-side fallback storage URLs must continue to work with the current Convex deployment setup.
+- The toolbar will no longer show the subscription tier on the canvas page.
+- Shared preset context must preserve current node behavior and save/remove flows.