chore(github): replace issue templates with issue forms

The Markdown bug and feature templates still asked "PWA or
Electron/Tauri application" with 0.16.0 as the example version, and
as free text they were mostly left unfilled: in the September backlog
triage only about a third of bug reports named the version or the
player, and 34 had to be sent back for a retest because they could
not be tied to a fix.

Replace them with GitHub issue forms that make the version, install
method, OS, source type and selected player required fields, ask
whether the problem is a regression, and point to Copy diagnostics.
Add a dedicated form for playback problems, the largest class of
reports, and a config that disables blank issues and links questions
to Discussions, the Docker guide and the website.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/ISSUE_TEMPLATE/playback_problem.yml

@@ -0,0 +1,152 @@
+name: ▶️ Playback problem
+description: A channel, movie or episode doesn't start, stops, stutters, or has no picture or sound.
+title: '[Playback]: '
+labels: ['bug :bug:']
+body:
+    - type: markdown
+      attributes:
+          value: |
+              Thanks for reporting a playback problem!
+
+              **Quick check first:** the built-in HTML5, Video.js and ArtPlayer players can't decode some codecs, for example HEVC/4K, AC3 or MPEG-2 video. Such streams usually play with **Embedded MPV** or an external **MPV** or **VLC** (**Settings → Playback → Video player**). Whether the stream plays there tells us a lot, so please mention it below.
+    - type: checkboxes
+      id: checks
+      attributes:
+          label: Before you submit
+          options:
+              - label: I'm on the latest release (or a nightly build) and the problem still happens there.
+                required: true
+              - label: I searched the [existing issues](https://github.com/4gray/iptvnator/issues?q=is%3Aissue) and this hasn't been reported yet.
+                required: true
+              - label: I removed usernames, passwords, MAC addresses, tokens and private URLs from everything I paste below.
+                required: true
+    - type: input
+      id: version
+      attributes:
+          label: IPTVnator version
+          description: Shown in **Settings → About**. For a nightly build, add the commit shown there too.
+          placeholder: 0.24.0
+      validations:
+          required: true
+    - type: dropdown
+      id: install
+      attributes:
+          label: How do you run IPTVnator?
+          options:
+              - Windows installer (.exe)
+              - macOS app (.dmg or .zip)
+              - macOS via Homebrew
+              - Linux AppImage
+              - Linux .deb, .rpm or pacman package
+              - Linux Snap
+              - Linux Flatpak
+              - Arch Linux AUR (iptvnator-bin)
+              - Self-hosted web app (Docker)
+              - Built from source
+      validations:
+          required: true
+    - type: input
+      id: os
+      attributes:
+          label: Operating system and version
+          description: For the self-hosted web app, add the browser you use as well.
+          placeholder: Windows 11 24H2 · macOS 26.6 on Apple Silicon · Ubuntu 24.04 · Docker on Unraid + Firefox
+      validations:
+          required: true
+    - type: dropdown
+      id: source
+      attributes:
+          label: Source type
+          options:
+              - M3U playlist
+              - Xtream Codes
+              - Stalker portal
+      validations:
+          required: true
+    - type: dropdown
+      id: content
+      attributes:
+          label: What were you playing?
+          options:
+              - Live TV channel
+              - Catch-up / archive programme
+              - Movie
+              - Series episode
+              - Radio station
+      validations:
+          required: true
+    - type: dropdown
+      id: player
+      attributes:
+          label: Video player
+          description: The player selected in **Settings → Playback → Video player**.
+          options:
+              - HTML5 video player
+              - Video.js player
+              - ArtPlayer
+              - Embedded MPV (Experimental)
+              - Embedded MPV with the frame-copy engine
+              - MPV player (external)
+              - VLC (external)
+      validations:
+          required: true
+    - type: dropdown
+      id: symptoms
+      attributes:
+          label: What goes wrong?
+          multiple: true
+          options:
+              - It doesn't start or keeps loading
+              - An error message appears
+              - It stops after a while
+              - It stutters or keeps buffering
+              - No picture, only sound
+              - No sound, or the wrong audio track
+              - Subtitles are missing or wrong
+              - Seeking or resuming goes to the wrong position
+              - Something else
+      validations:
+          required: true
+    - type: dropdown
+      id: elsewhere
+      attributes:
+          label: Does the same stream play elsewhere?
+          options:
+              - Yes, with another player in IPTVnator
+              - Yes, in VLC or another app outside IPTVnator
+              - No, it fails everywhere I tried
+              - I haven't tried
+      validations:
+          required: true
+    - type: dropdown
+      id: regression
+      attributes:
+          label: Did this work in an earlier version?
+          options:
+              - Yes, it worked in an earlier version
+              - No, it never worked for me
+              - I don't know
+      validations:
+          required: true
+    - type: input
+      id: last-working-version
+      attributes:
+          label: Last version where it worked
+          description: Only if it worked before.
+          placeholder: 0.23.0
+    - type: textarea
+      id: what-happened
+      attributes:
+          label: What happened?
+          description: |
+              Describe what you see and when. If it stops, roughly after how long?
+              Mention the stream format if you know it (HLS .m3u8, MPEG-TS .ts, DASH .mpd, MKV…). Please don't paste full stream URLs that contain credentials or tokens.
+      validations:
+          required: true
+    - type: textarea
+      id: diagnostics
+      attributes:
+          label: Diagnostics, logs and screenshots
+          description: |
+              If an error screen appears, click **Copy diagnostics** and paste the report here; it contains no stream URLs or credentials.
+              If playback starts, the values from **Stream info** in the player overlay help too. Screenshots and short recordings are welcome.