feat: rename to FabledScryer, multi-dashboard system, plugin management, branding

- Rename package fablednetmon → fabledscryer throughout
- Multi-dashboard: ownership, per-user defaults, HTMX edit (add/remove/reorder)
- Read-only share tokens scoped to individual dashboards
- Dashboard edit is HTMX-driven (no page reloads)
- Plugin management system: remote catalog, download/install, hot-reload, in-app restart
- plugin_index.py: fetch/cache remote index.yaml; default URL → bvandeusen/fabledscryer-plugins
- plugin_manager.py: download_and_install_plugin, hot_reload_plugin, restart_app
  - ZIP extraction handles GitHub archive formats (name-v1.0.0/, name-main/)
- Settings split into tabbed sections: General, Notifications, Ansible, Plugins
- Plugins tab: catalog browser (HTMX), install/activate/update/restart actions
- UI/branding: dark palette (#07071a), crystal ball SVG logo, animated star field,
  Libertinus Serif applied to headings, nav, labels, and section titles
- Widget registry (core/widgets.py) for dashboard plugin integration
- UPS widget.html (dashboard card) and settings/_tabs.html include
- Migrations 0005–0008: dashboards, is_default, ownership, share tokens
- docs/plugins/: writing-a-plugin.md updated with publishing guide,
  index.yaml.example template for fabledscryer-plugins repo

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

fabledscryer/core/time_range.py

@@ -0,0 +1,44 @@
+# fabledscryer/core/time_range.py
+"""Shared time-range utilities for scoping queries and sparkline data."""
+from __future__ import annotations
+from datetime import datetime, timedelta, timezone
+from typing import TypeVar
+
+RANGES: dict[str, timedelta] = {
+    "1h":  timedelta(hours=1),
+    "6h":  timedelta(hours=6),
+    "24h": timedelta(hours=24),
+    "7d":  timedelta(days=7),
+    "30d": timedelta(days=30),
+}
+
+RANGE_OPTIONS: list[str] = list(RANGES.keys())
+DEFAULT_RANGE = "24h"
+
+
+def parse_range(range_str: str | None) -> tuple[datetime, str]:
+    """Return (since_datetime, range_key) from a query-param string like '24h'."""
+    key = range_str if range_str in RANGES else DEFAULT_RANGE
+    since = datetime.now(timezone.utc) - RANGES[key]
+    return since, key
+
+
+def bucket_seconds(since: datetime, target_points: int = 80) -> int:
+    """Return bucket width in seconds so that (now - since) / width ≈ target_points.
+
+    Minimum is 60s (one poll interval) so raw data is never re-averaged below
+    the collection resolution.
+    """
+    range_secs = (datetime.now(timezone.utc) - since).total_seconds()
+    return max(60, int(range_secs / target_points))
+
+
+T = TypeVar("T")
+
+
+def subsample(seq: list[T], n: int = 80) -> list[T]:
+    """Return at most n evenly-distributed elements from seq (preserves order)."""
+    if len(seq) <= n:
+        return seq
+    indices = sorted({int(round(i * (len(seq) - 1) / (n - 1))) for i in range(n)})
+    return [seq[i] for i in indices]