Add resizable room panel, searchable user picker, and direct room membership

Room info panel is now user-resizable (fixing a layout clip at narrow
widths), and every user-selection spot (room membership, admin ownership
transfer) uses a new searchable UserPicker instead of raw text input or
prompt(). Member rows fold role + actions into a single inline dropdown
instead of a row of buttons, so the member list stays usable as rooms grow.

Room invites (the accept/decline flow) are replaced by adding a user to a
room directly -- an admin/owner picks someone and they're a member
immediately, with a "you've been added" notification email instead of an
invite email. Drops the now-unused room_invites table.

backend/app/models/__init__.py

@@ -2,7 +2,7 @@ from app.models.admin_audit_log import AdminAuditLog
 from app.models.api_token import ApiToken
 from app.models.base import Base
 from app.models.event_subscription import EventSubscription
-from app.models.invite import InviteStatus, RoomInvite
+from app.models.invite import InviteStatus
 from app.models.membership import RoomMembership, RoomRole
 from app.models.message import Message
 from app.models.message_image import MessageImage
@@ -23,7 +23,6 @@ __all__ = [
     "Message",
     "MessageImage",
     "MessageReaction",
-    "RoomInvite",
     "InviteStatus",
     "SiteInvite",
     "SmtpSettings",

backend/app/models/invite.py

@@ -1,53 +1,7 @@
 import enum
-import uuid
-from datetime import datetime, timedelta, timezone
-
-from sqlalchemy import CheckConstraint, DateTime, Enum, ForeignKey, String, func
-from sqlalchemy.orm import Mapped, mapped_column, relationship
-
-from app.models.base import Base
-
-DEFAULT_INVITE_LIFETIME = timedelta(days=7)
-
-
-def _default_expires_at() -> datetime:
-    return datetime.now(timezone.utc) + DEFAULT_INVITE_LIFETIME
 
 
 class InviteStatus(str, enum.Enum):
     pending = "pending"
     accepted = "accepted"
     revoked = "revoked"
-
-
-class RoomInvite(Base):
-    __tablename__ = "room_invites"
-    __table_args__ = (
-        CheckConstraint(
-            "target_user_id IS NOT NULL OR target_email IS NOT NULL",
-            name="room_invites_target_required",
-        ),
-    )
-
-    id: Mapped[uuid.UUID] = mapped_column(primary_key=True, default=uuid.uuid4)
-    room_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("rooms.id"), index=True, nullable=False)
-    invited_by: Mapped[uuid.UUID] = mapped_column(ForeignKey("users.id"), nullable=False)
-    token: Mapped[str] = mapped_column(String(64), unique=True, index=True, nullable=False)
-    target_user_id: Mapped[uuid.UUID | None] = mapped_column(ForeignKey("users.id"), index=True)
-    # Stored per the documented schema but not actionable yet: there's no
-    # email-delivery mechanism anywhere in the stack. Phase 2 only creates
-    # invites via target_user_id (existing users, looked up by username).
-    target_email: Mapped[str | None] = mapped_column(String(255))
-    expires_at: Mapped[datetime] = mapped_column(
-        DateTime(timezone=True), default=_default_expires_at, nullable=False
-    )
-    status: Mapped[InviteStatus] = mapped_column(
-        Enum(InviteStatus, name="invite_status"), default=InviteStatus.pending, nullable=False
-    )
-    created_at: Mapped[datetime] = mapped_column(
-        DateTime(timezone=True), server_default=func.now(), nullable=False
-    )
-
-    room = relationship("Room")
-    inviter = relationship("User", foreign_keys=[invited_by])
-    target_user = relationship("User", foreign_keys=[target_user_id])

backend/app/models/site_invite.py

@@ -16,7 +16,7 @@ def _default_expires_at() -> datetime:
 
 class SiteInvite(Base):
     """An admin-issued invite for someone with no account yet -- distinct
-    from RoomInvite, which targets an existing user for a specific room."""
+    from adding an existing user directly to a room."""
 
     __tablename__ = "site_invites"