feat: hydration logging and daily goal ring

Add a WATER_INTAKE measurement type and a per-user daily goal so the
Insights overview can track water intake against a goal ring. Logging
rides the existing measurements create path (type WATER_INTAKE, unit ml,
summed cumulatively); GET/PATCH /api/hydration read the day total and own
the goal. The goal-ring math (empty / partial / met / exceeded) lives in
a pure helper, free of Prisma and React, and is unit-tested in isolation.

Wire the new type through the measurement enum, value ranges, cumulative
HealthKit handling, categories, display transform, list metadata, record
direction, and the chartable-token allowlist. The HealthKit DietaryWater
import stays on the nutrition hold, so the type carries no import mapping
by design.

Document GET/PATCH /api/hydration in the OpenAPI contract.

src/lib/openapi/registry.ts

@@ -77,6 +77,7 @@ const openApiBase: Pick<
     { name: "Illness" },
     { name: "Admin" },
     { name: "Meta" },
+    { name: "Hydration" },
   ],
 };
 

src/lib/openapi/routes/hydration.ts

@@ -0,0 +1,102 @@
+/**
+ * OpenAPI route module — hydration daily-goal surface (v1.25).
+ *
+ * `GET /api/hydration` reads today's summed water intake vs the user's goal;
+ * `PATCH /api/hydration` sets the per-user daily goal. Logging rides the
+ * measurements create path (POST /api/measurements, type WATER_INTAKE), so it
+ * is documented there, not here.
+ *
+ * Part of the OpenAPI route table; aggregated in `./index.ts`.
+ */
+import { z } from "zod/v4";
+import type { ZodOpenApiObject } from "zod-openapi";
+
+import { dataEnvelope, stdResponses } from "./shared";
+
+const hydrationEntry = z.object({
+  id: z.string(),
+  value: z.number().describe("Logged amount in millilitres."),
+  measuredAt: z.string().describe("ISO-8601 instant the entry was logged."),
+});
+
+const hydrationTodayResponse = z
+  .object({
+    date: z.string().describe("ISO-8601 start of the user's local day."),
+    totalMl: z.number().describe("Today's summed intake in ml."),
+    goalMl: z.number().describe("Effective daily goal in ml."),
+    percent: z.number().describe("Progress toward the goal, capped at 100."),
+    rawPercent: z.number().describe("Uncapped progress; can exceed 100."),
+    met: z.boolean().describe("Whether the day's total reached the goal."),
+    remainingMl: z.number().describe("Remaining ml to the goal (0 once met)."),
+    entries: z.array(hydrationEntry),
+  })
+  .meta({
+    id: "HydrationToday",
+    description: "Today's water-intake total vs the user's daily goal.",
+  });
+
+const hydrationGoalRequest = z
+  .object({
+    goalMl: z
+      .number()
+      .int()
+      .min(250)
+      .max(8000)
+      .describe("Daily hydration goal in millilitres."),
+  })
+  .meta({
+    id: "HydrationGoalRequest",
+    description: "Set the per-user daily hydration goal (ml).",
+  });
+
+const hydrationGoalResponse = z
+  .object({ goalMl: z.number() })
+  .meta({ id: "HydrationGoalResponse" });
+
+export const hydrationPaths: NonNullable<ZodOpenApiObject["paths"]> = {
+  "/api/hydration": {
+    get: {
+      tags: ["Hydration"],
+      summary: "Today's hydration total vs goal",
+      description:
+        "Sums the calling user's WATER_INTAKE measurements for the current local day and compares them against the per-user goal (default 2000 ml).",
+      responses: {
+        "200": {
+          description: "Today's hydration summary.",
+          content: {
+            "application/json": {
+              schema: dataEnvelope(
+                hydrationTodayResponse,
+                "HydrationTodayEnvelope",
+              ),
+            },
+          },
+        },
+        ...stdResponses,
+      },
+    },
+    patch: {
+      tags: ["Hydration"],
+      summary: "Set the daily hydration goal",
+      description: "Updates the per-user daily hydration goal in millilitres.",
+      requestBody: {
+        required: true,
+        content: { "application/json": { schema: hydrationGoalRequest } },
+      },
+      responses: {
+        "200": {
+          description: "Goal updated.",
+          content: {
+            "application/json": {
+              schema: dataEnvelope(
+                hydrationGoalResponse,
+                "HydrationGoalEnvelope",
+              ),
+            },
+          },
+        },
+        ...stdResponses,
+      },
+    },
+  },
+};