feat: 补齐 Garmin 未同步的数据，并各自配上界面

审计 57 个接口后，把账号里真有数据却从未入库的部分补上。全部走同步模块，
界面只读本地库。

新增数据
- 体重与身体成分（体脂率/肌肉量/体水分/骨量/内脏脂肪/代谢年龄）
- 血压（接口通，账号暂无记录）
- 跑步成绩预测（5 公里 / 10 公里 / 半马 / 全马）
- 爬坡分、饮水量、出汗量 → health_data 新增七列
- 全天曲线：心率 / 压力 / 身体电量 / 呼吸 / 血氧
- 挑战赛（徽章挑战与好友挑战，与一次性的徽章不同，有周期和进度）
- 已配对设备

新增界面
- /body/ 身体成分：体重大数字 + BMI 分级 + 体脂肌肉曲线 + 血压表格
- /race/ 成绩预测：四个距离的预测成绩与配速，以及预测随时间的变化
- /challenges/ 挑战赛：按类型筛选，有目标的显示进度条
- /devices/ 已配对设备
- 每日页新增「全天曲线」，这是存日内采样的主要目的
- 健康页新增「身体成分」分组与「更多」入口，运动页加挑战赛与成绩预测入口

同步开销
- 日内曲线每天五个请求，14 天以内的同步顺带拉，更长的历史交给后台
  「补齐详细数据」，否则一年的同步会多出约 1800 个请求
- 原来的「补齐运动详情」扩展为统一的补齐任务，分阶段上报进度

日内采样抽稀到每天 240 点：手机图表分辨不出更多，只会把行撑大。

全量 446 项测试通过。

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

backend/db.py

@@ -188,6 +188,97 @@ CREATE TABLE IF NOT EXISTS activity_details (
   FOREIGN KEY (user_id) REFERENCES users(id)
 );
 
+-- Weight and body composition, one row per measurement day.
+-- Separate from health_data because it arrives from the scale rather than the
+-- watch, on its own irregular schedule — most days simply have no row.
+CREATE TABLE IF NOT EXISTS body_composition (
+  id VARCHAR(96) PRIMARY KEY,
+  user_id VARCHAR(64) NOT NULL,
+  date DATE NOT NULL,
+  weight_kg DOUBLE,
+  bmi DOUBLE,
+  body_fat_pct DOUBLE,
+  body_water_pct DOUBLE,
+  bone_mass_kg DOUBLE,
+  muscle_mass_kg DOUBLE,
+  physique_rating DOUBLE,
+  visceral_fat DOUBLE,
+  metabolic_age DOUBLE,
+  source VARCHAR(32),
+  UNIQUE(user_id, date),
+  FOREIGN KEY (user_id) REFERENCES users(id)
+);
+
+-- Blood pressure readings. Manually entered in Garmin Connect, so there may
+-- be none at all; the table exists so that there is somewhere to put them.
+CREATE TABLE IF NOT EXISTS blood_pressure (
+  id VARCHAR(96) PRIMARY KEY,
+  user_id VARCHAR(64) NOT NULL,
+  measured_at DATETIME NOT NULL,
+  systolic INT,
+  diastolic INT,
+  pulse INT,
+  note TEXT,
+  UNIQUE(user_id, measured_at),
+  FOREIGN KEY (user_id) REFERENCES users(id)
+);
+
+-- Garmin's predicted race times, in seconds. One row per day it recalculates.
+CREATE TABLE IF NOT EXISTS race_predictions (
+  id VARCHAR(96) PRIMARY KEY,
+  user_id VARCHAR(64) NOT NULL,
+  date DATE NOT NULL,
+  time_5k INT,
+  time_10k INT,
+  time_half INT,
+  time_marathon INT,
+  UNIQUE(user_id, date),
+  FOREIGN KEY (user_id) REFERENCES users(id)
+);
+
+-- Within-day sample series: heart rate, stress, body battery, respiration,
+-- SpO2. One generic table rather than five near-identical ones — they differ
+-- only in what the numbers mean, and the daily screen reads them the same way.
+CREATE TABLE IF NOT EXISTS daily_series (
+  id VARCHAR(96) PRIMARY KEY,
+  user_id VARCHAR(64) NOT NULL,
+  date DATE NOT NULL,
+  kind VARCHAR(32) NOT NULL,
+  payload MEDIUMTEXT,
+  fetched_at DATETIME,
+  UNIQUE(user_id, date, kind),
+  FOREIGN KEY (user_id) REFERENCES users(id)
+);
+
+-- Badge challenges and ad-hoc challenges. Distinct from `badges`: a badge is
+-- earned once, a challenge has a period, a target and a standing.
+CREATE TABLE IF NOT EXISTS challenges (
+  id VARCHAR(96) PRIMARY KEY,
+  user_id VARCHAR(64) NOT NULL,
+  challenge_uuid VARCHAR(96),
+  kind VARCHAR(32),
+  name VARCHAR(255),
+  status VARCHAR(64),
+  start_date DATE,
+  end_date DATE,
+  payload MEDIUMTEXT,
+  FOREIGN KEY (user_id) REFERENCES users(id)
+);
+
+-- Paired devices, so the app can say which watch a number came from.
+CREATE TABLE IF NOT EXISTS devices (
+  id VARCHAR(96) PRIMARY KEY,
+  user_id VARCHAR(64) NOT NULL,
+  device_id VARCHAR(96),
+  name VARCHAR(255),
+  model VARCHAR(255),
+  serial VARCHAR(96),
+  software_version VARCHAR(64),
+  last_used_at DATETIME,
+  payload MEDIUMTEXT,
+  FOREIGN KEY (user_id) REFERENCES users(id)
+);
+
 -- One cached LLM answer per user. Generating one takes minutes against a
 -- large reasoning model, which is far too slow to sit in a page load, so the
 -- result is stored and reused until the underlying data changes.
@@ -349,6 +440,15 @@ MIGRATIONS = {
         ("training_readiness", "INT"),
         ("vo2max", "DOUBLE"),
         ("endurance_score", "INT"),
+        # hill score, hydration and weight — daily scalars that were being
+        # fetched from Garmin by nothing at all until now
+        ("hill_score", "INT"),
+        ("hydration_ml", "INT"),
+        ("hydration_goal_ml", "INT"),
+        ("sweat_loss_ml", "INT"),
+        ("weight_kg", "DOUBLE"),
+        ("body_fat_pct", "DOUBLE"),
+        ("bmi", "DOUBLE"),
     ],
 }