refactor: ComfyUI Agent with structured parsing + image gen + TTS

- New system prompt with 【CHARACTER】【SCENE】【TTS】【WORKFLOW】 markers
- Backend parses structured sections, auto-calls gpt-image-2 for character/scene images
- Auto-calls TTS API for dialogue lines
- Case-insensitive field parsing, robust whitespace handling
- Static file serving with SPA fallback for frontend
- No Node.js runtime dependency for serving

boosapi-rs/migrations/20260518000001_usage_logs.sql

@@ -0,0 +1,37 @@
+-- Usage tracking tables migrated from the Node.js backend.
+
+CREATE TABLE IF NOT EXISTS usage_logs (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    downstream_key_id INTEGER,
+    model TEXT,
+    prompt_tokens INTEGER DEFAULT 0,
+    completion_tokens INTEGER DEFAULT 0,
+    total_tokens INTEGER DEFAULT 0,
+    cost REAL DEFAULT 0.0,
+    created_at TEXT DEFAULT (datetime('now')),
+    FOREIGN KEY (downstream_key_id) REFERENCES downstream_api_keys(id) ON DELETE SET NULL
+);
+
+CREATE INDEX IF NOT EXISTS usage_logs_downstream_key_created_idx
+    ON usage_logs (downstream_key_id, created_at);
+
+CREATE INDEX IF NOT EXISTS usage_logs_created_idx
+    ON usage_logs (created_at);
+
+CREATE TABLE IF NOT EXISTS usage_daily_snapshots (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    local_day TEXT NOT NULL,
+    downstream_key_id INTEGER,
+    request_count INTEGER NOT NULL DEFAULT 0,
+    prompt_tokens INTEGER NOT NULL DEFAULT 0,
+    completion_tokens INTEGER NOT NULL DEFAULT 0,
+    total_tokens INTEGER NOT NULL DEFAULT 0,
+    total_cost REAL NOT NULL DEFAULT 0.0,
+    created_at TEXT DEFAULT (datetime('now')),
+    updated_at TEXT DEFAULT (datetime('now')),
+    UNIQUE(local_day, downstream_key_id),
+    FOREIGN KEY (downstream_key_id) REFERENCES downstream_api_keys(id) ON DELETE SET NULL
+);
+
+CREATE INDEX IF NOT EXISTS usage_daily_snapshots_day_idx
+    ON usage_daily_snapshots (local_day);