feat: let a subscription carry clip bounds (closes #1049)

A subscription already carries every other download option and applies it to
each video it queues. Clip bounds were the one exception: 4f83174 added them
for one-off downloads and carved subscriptions out, rejecting the fields in the
subscribe route and stripping them in the UI before the request was built. So
the fields sat visible in the shared advanced-options panel while quietly doing
nothing for a subscription.

Carry them like the rest: two fields on SubscriptionInfo, threaded through the
check flow to add_entry. Stored records that predate the fields take the
defaults, since _from_stored filters by field name.

One thing does not carry over. parse_download_options reads a YouTube t=
timestamp from the URL and turns it into a clip start, which is right when you
paste a link to a moment in a video you want. A subscription URL is a channel
or a playlist, so a timestamp left on it says nothing about the videos that
feed will yield, and honouring it would silently truncate every future
download. The subscribe route therefore takes clip bounds only when the caller
sent the fields explicitly; the t= param is still stripped from the stored URL.

Worth knowing when using this: the range is a fixed offset applied to every
video, so it suits feeds with a consistent shape - a standing intro, a fixed
sponsor read - and will cut in the wrong place on a feed without one.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

app/subscriptions.py

@@ -189,6 +189,13 @@ class SubscriptionInfo:
     ytdl_options_overrides: dict[str, Any] = field(default_factory=dict)
     title_regex: str = ""
     skip_subscriber_only: bool = False
+    # A fixed range applied to every video the subscription downloads. Only
+    # sensible for channels with a consistent format (a standing intro, a fixed
+    # sponsor read); left unset, videos download whole. Old stored records
+    # predate these fields and take the defaults — _from_stored filters by
+    # field name, so nothing needs migrating.
+    clip_start: Optional[float] = None
+    clip_end: Optional[float] = None
     last_checked: Optional[float] = None
     seen_ids: list[str] = field(default_factory=list)
     error: Optional[str] = None
@@ -211,6 +218,8 @@ class SubscriptionInfo:
             "folder": self.folder,
             "title_regex": self.title_regex,
             "skip_subscriber_only": self.skip_subscriber_only,
+            "clip_start": self.clip_start,
+            "clip_end": self.clip_end,
             "last_checked": self.last_checked,
             "seen_count": len(self.seen_ids),
             "error": self.error,
@@ -240,6 +249,8 @@ def _subscription_to_record(sub: SubscriptionInfo) -> dict[str, Any]:
         "ytdl_options_overrides": sub.ytdl_options_overrides,
         "title_regex": sub.title_regex,
         "skip_subscriber_only": sub.skip_subscriber_only,
+        "clip_start": sub.clip_start,
+        "clip_end": sub.clip_end,
         "last_checked": sub.last_checked,
         "seen_ids": list(sub.seen_ids),
         "error": sub.error,
@@ -474,6 +485,8 @@ class SubscriptionManager:
         subtitle_mode: str,
         ytdl_options_presets: Optional[list[str]] = None,
         ytdl_options_overrides: Optional[dict[str, Any]] = None,
+        clip_start: Optional[float] = None,
+        clip_end: Optional[float] = None,
     ) -> tuple[list[str], list[str]]:
         queued_ids: list[str] = []
         queue_errors: list[str] = []
@@ -504,6 +517,8 @@ class SubscriptionManager:
                 subtitle_mode,
                 presets,
                 ytdl_options_overrides,
+                clip_start,
+                clip_end,
             )
             if isinstance(result, dict) and result.get("status") == "error":
                 msg = str(result.get("msg") or f"Queueing failed for {vurl}")
@@ -593,6 +608,8 @@ class SubscriptionManager:
         ytdl_options_overrides: Optional[dict[str, Any]] = None,
         title_regex: Any = None,
         skip_subscriber_only: Any = None,
+        clip_start: Optional[float] = None,
+        clip_end: Optional[float] = None,
     ) -> dict:
         url = self._normalize_url(url)
         if not url:
@@ -679,6 +696,8 @@ class SubscriptionManager:
                 ytdl_options_overrides=dict(ytdl_options_overrides or {}),
                 title_regex=title_regex_stored,
                 skip_subscriber_only=skip_so,
+                clip_start=clip_start,
+                clip_end=clip_end,
                 last_checked=time.time(),
                 seen_ids=list(dict.fromkeys(all_ids)),
                 error=None,
@@ -930,6 +949,8 @@ class SubscriptionManager:
             dl_ytdl_overrides = dict(cur.ytdl_options_overrides)
             dl_title_regex = cur.title_regex or ""
             dl_skip_subscriber_only = bool(cur.skip_subscriber_only)
+            dl_clip_start = cur.clip_start
+            dl_clip_end = cur.clip_end
 
         new_entries: list[dict] = []
         for ent in entries:
@@ -994,6 +1015,8 @@ class SubscriptionManager:
             subtitle_mode=dl_submode,
             ytdl_options_presets=dl_ytdl_presets,
             ytdl_options_overrides=dl_ytdl_overrides,
+            clip_start=dl_clip_start,
+            clip_end=dl_clip_end,
         )
         log.info(
             "Subscription check finished for %s: %d new, %d filtered, %d subscriber_skipped, %d queued, %d failed",