feat: Steam account integration (link account, sync achievements & library)

[LED-N]

What this PR does

Adds full Steam account integration to Hydra, allowing users to:

• Link their Steam account via Steam OpenID 2.0 (ownership verified, not just SteamID lookup)
• Import achievements for individual Steam games from the game's achievement page
• Batch sync all achievements across the entire Hydra library, with smart rate-limit retry (no fixed delay — only pauses on HTTP 429)
• Sync Steam library — imports all owned Steam games with correct playtime (takes the highest value between Steam and Hydra) and icons from the Steam CDN
• Library source filter — filter your library by All / Steam imported / Hydra only
• Non-blocking UX — progress modals are closeable while sync continues in background, with a cancel button
• Steam display name + avatar shown in settings instead of raw SteamID64
• Auto-sync on startup — optional checkbox in settings
• EN + FR translations included

Technical notes

• Rate limiting: requests fire as fast as possible; on HTTP 429, exponential backoff (5s → 10s → 15s, up to 3 retries) instead of a fixed per-request delay.
• Playtime sync uses the absolute /playtime endpoint so the profile page reflects the correct value.
• A Steam Web API key is required per user (free at steamcommunity.com/dev/apikey) — no shared key is possible due to Valve ToS and per-key rate limits.

Notes on Steam authentication

Steam login uses the OpenID 2.0 flow with a temporary local HTTP server
as the callback endpoint (openid.realm = http://127.0.0.1:<random_port>).
This is the standard approach for desktop applications — Valve explicitly
supports 127.0.0.1 as a valid realm. As a result, Steam's login page
displays "Sign in through 127.0.0.1" to the user, which is expected
behavior for native apps.

If the team would prefer to show a branded domain (e.g. hydralauncher.gg),
this would require routing the OpenID callback through a backend endpoint
and returning the SteamID to the app via a custom protocol link
(hydra://steam-auth?steamid=...). Happy to explore this if preferred,
but kept the self-contained local server approach for simplicity.

Checklist (from PR template)

• I have read the Hydra documentation
• I have checked that there are no duplicate pull requests related to this request
• I have considered, and confirm that this submission is valuable to others
• I accept that this submission may not be used and the pull request may be closed at the discretion of the maintainers

Screenshots

Settings — Steam integration (Not yet linked)

Settings — Steam integration (Linking)

Settings — Steam integration (Linked)

Library source filter

Sync progress modal

Sync from Steam button (achievements)

[sonarqubecloud]

Quality Gate passed

Issues
15 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[DevOxofdev]

Ca a l air vraiment pas mal